├── .gitignore ├── CMakeLists.txt ├── COPYING ├── README.md ├── ext ├── CMakeLists.txt └── download-dependencies.sh └── src ├── CMakeLists.txt ├── headless ├── CMakeLists.txt └── SkiaExampleHeadless.cpp └── qt ├── CMakeLists.txt ├── SkiaExampleQt.cpp ├── SkiaPolygonWidget.cpp └── SkiaPolygonWidget.h /.gitignore: -------------------------------------------------------------------------------- 1 | /CMakeLists.txt.user 2 | /ext/skia/ 3 | -------------------------------------------------------------------------------- /CMakeLists.txt: -------------------------------------------------------------------------------- 1 | project(SkiaDemo) 2 | cmake_minimum_required(VERSION 3.0) 3 | 4 | # Set C++ standard. The SDK containers currently have CMake 3.0.2 which 5 | # does not support target property CXX_STANDARD and friends. So just pass 6 | # it as compile option. 7 | add_compile_options(-std=c++11) 8 | 9 | find_package(PkgConfig) 10 | find_package(PNG REQUIRED) 11 | find_library(LIBPTHREAD pthread) 12 | if (NOT LIBPTHREAD) 13 | message(FATAL_ERROR "Can't find libpthread") 14 | endif() 15 | 16 | add_subdirectory(ext) 17 | add_subdirectory(src) 18 | -------------------------------------------------------------------------------- /COPYING: -------------------------------------------------------------------------------- 1 | GNU GENERAL PUBLIC LICENSE 2 | Version 3, 29 June 2007 3 | 4 | Copyright (C) 2007 Free Software Foundation, Inc. 5 | Everyone is permitted to copy and distribute verbatim copies 6 | of this license document, but changing it is not allowed. 7 | 8 | Preamble 9 | 10 | The GNU General Public License is a free, copyleft license for 11 | software and other kinds of works. 12 | 13 | The licenses for most software and other practical works are designed 14 | to take away your freedom to share and change the works. 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Interpretation of Sections 15 and 16. 613 | 614 | If the disclaimer of warranty and limitation of liability provided 615 | above cannot be given local legal effect according to their terms, 616 | reviewing courts shall apply local law that most closely approximates 617 | an absolute waiver of all civil liability in connection with the 618 | Program, unless a warranty or assumption of liability accompanies a 619 | copy of the Program in return for a fee. 620 | 621 | END OF TERMS AND CONDITIONS 622 | 623 | How to Apply These Terms to Your New Programs 624 | 625 | If you develop a new program, and you want it to be of the greatest 626 | possible use to the public, the best way to achieve this is to make it 627 | free software which everyone can redistribute and change under these terms. 628 | 629 | To do so, attach the following notices to the program. It is safest 630 | to attach them to the start of each source file to most effectively 631 | state the exclusion of warranty; and each file should have at least 632 | the "copyright" line and a pointer to where the full notice is found. 633 | 634 | 635 | Copyright (C) 636 | 637 | This program is free software: you can redistribute it and/or modify 638 | it under the terms of the GNU General Public License as published by 639 | the Free Software Foundation, either version 3 of the License, or 640 | (at your option) any later version. 641 | 642 | This program is distributed in the hope that it will be useful, 643 | but WITHOUT ANY WARRANTY; without even the implied warranty of 644 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 645 | GNU General Public License for more details. 646 | 647 | You should have received a copy of the GNU General Public License 648 | along with this program. If not, see . 649 | 650 | Also add information on how to contact you by electronic and paper mail. 651 | 652 | If the program does terminal interaction, make it output a short 653 | notice like this when it starts in an interactive mode: 654 | 655 | Copyright (C) 656 | This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. 657 | This is free software, and you are welcome to redistribute it 658 | under certain conditions; type `show c' for details. 659 | 660 | The hypothetical commands `show w' and `show c' should show the appropriate 661 | parts of the General Public License. Of course, your program's commands 662 | might be different; for a GUI interface, you would use an "about box". 663 | 664 | You should also get your employer (if you work as a programmer) or school, 665 | if any, to sign a "copyright disclaimer" for the program, if necessary. 666 | For more information on this, and how to apply and follow the GNU GPL, see 667 | . 668 | 669 | The GNU General Public License does not permit incorporating your program 670 | into proprietary programs. If your program is a subroutine library, you 671 | may consider it more useful to permit linking proprietary applications with 672 | the library. If this is what you want to do, use the GNU Lesser General 673 | Public License instead of this License. But first, please read 674 | . 675 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # Skia Example Project 2 | 3 | This is an example CMake-based project that integrates Skia. A headless and a Qt Widgets example are provided. The headless example `skia_example_headless` just creates a `test.png` in the current working directory using Skia. The Qt example `skia_example_qt` creates a window with a Skia-based widget drawing a polygon. 4 | 5 | There is probably quite some space to optimize the Skia config and the Qt wrapping. But I hope this can serve as a starting point. 6 | 7 | After checking out this repository run `ext/download-dependencies.sh` to get Skia sources. Only then run CMake to configure the project. 8 | -------------------------------------------------------------------------------- /ext/CMakeLists.txt: -------------------------------------------------------------------------------- 1 | cmake_minimum_required(VERSION 3.0) 2 | include(ExternalProject) 3 | 4 | # 5 | # Skia 6 | # 7 | 8 | # case-insensitive match TODO: is debug, Debug, DEBUG all valid? 9 | if (CMAKE_BUILD_TYPE MATCHES "[dD][eE][bB][uU][gG]") 10 | set(IS_DEBUG_BUILD ON) 11 | else () 12 | set(IS_DEBUG_BUILD OFF) 13 | endif () 14 | 15 | # I wanted to expose (almost) all Skia options as CMake options but sadly 16 | # GN is a really bad tool - It produces non-overridable configure errors like: 17 | # 18 | # The variable "skia_use_system_libjpeg_turbo" was set as a build argument but never appeared in a declare_args() block in any buildfile. 19 | # 20 | # ... even though the option exists (this one in skia/third_party/libjpeg-turbo/BUILD.gb) 21 | # and it's listed in gn args --list. 22 | # (It seems to be caused by the fact that some options are only actually used when other 23 | # options are set appropriately. But it's not always obvious - one would have to dig into 24 | # Skia configuration. And replicating the dependencies here + propagating it correctly into 25 | # the ExternalProject setup is beyond reasonable. 26 | option(EXT_SKIA_ALWAYS_BUILD "" OFF) 27 | option(EXT_SKIA_DEBUG "" ${IS_DEBUG_BUILD}) 28 | option(EXT_SKIA_SHARED "build a shared lbrary (ON) or a static library (OFF)" OFF) 29 | 30 | set(SKIA_SRC "${CMAKE_CURRENT_SOURCE_DIR}/skia") 31 | 32 | if (NOT EXISTS ${SKIA_SRC}) 33 | message(FATAL_ERROR "Can't find Skia sources. Please run download-dependencies.sh.") 34 | endif () 35 | 36 | set(SKIA_BUILD_DIR "${CMAKE_CURRENT_BINARY_DIR}/skia") 37 | 38 | # Skia comes with -Werror on by default. That's a cool feature for release... 39 | set(SKIA_C_FLAGS -Wno-error ${CMAKE_C_FLAGS}) 40 | set(SKIA_CXX_FLAGS -Wno-error ${CMAKE_CXS_FLAGS}) 41 | 42 | function(SET_SKIA_CONFIG_OPTION OPT_NAME OPT_VALUE) 43 | if (OPT_VALUE) 44 | set(${OPT_NAME} "true" PARENT_SCOPE) 45 | else () 46 | set(${OPT_NAME} "false" PARENT_SCOPE) 47 | endif () 48 | endfunction() 49 | 50 | SET_SKIA_CONFIG_OPTION(SK_CONF_DEBUG ${EXT_SKIA_DEBUG}) 51 | SET_SKIA_CONFIG_OPTION(SK_CONF_SHARED ${EXT_SKIA_SHARED}) 52 | 53 | # it's not possible to enable both OFFICIAL and DEBUG 54 | if (EXT_SKIA_OFFICIAL_BUILD AND NOT EXT_SKIA_DEBUG) 55 | set(SK_CONF_IS_OFFICIAL_BUILD "true") 56 | else () 57 | set(SK_CONF_IS_OFFICIAL_BUILD "false") 58 | endif () 59 | 60 | ExternalProject_Add(SKIA_build 61 | # This is needed for list expansion of C(XX)_FLAGS. 62 | LIST_SEPARATOR "," 63 | SOURCE_DIR ${SKIA_SRC} 64 | CONFIGURE_COMMAND ${SKIA_SRC}/bin/gn gen --root=${SKIA_SRC} ${SKIA_BUILD_DIR} 65 | # getting right the wonky cmake string handling (with the extra level of ExternalProject) 66 | # and the undocumented args handling of GN is a special treat 67 | # at least Cmake 3.0 has the line continuation feature wich is cool 68 | # but then the args can't be indented because GN is written by somone with overly strong opinions: 69 | # "You got a tab character in here. Tabs are evil. Convert to spaces." 70 | "--args=\ 71 | ar=\"${CMAKE_AR}\" \ 72 | cc=\"${CMAKE_C_COMPILER}\" \ 73 | cxx=\"${CMAKE_CXX_COMPILER}\" \ 74 | extra_cflags_c=[\"${SKIA_C_FLAGS}\"] \ 75 | extra_cflags_cc=[\"${SKIA_CXX_FLAGS}\"] \ 76 | is_official_build=${SK_CONF_IS_OFFICIAL_BUILD} \ 77 | is_component_build=${SK_CONF_SHARED} \ 78 | is_debug=${SK_CONF_DEBUG} \ 79 | skia_enable_gpu=true \ 80 | skia_use_egl=false \ 81 | skia_use_vulkan=false \ 82 | skia_enable_vulkan_debug_layers=false \ 83 | skia_enable_spirv_validation=false \ 84 | skia_use_icu=true \ 85 | skia_use_system_icu=true \ 86 | skia_use_expat=true \ 87 | skia_use_system_expat=true \ 88 | skia_use_libjpeg_turbo=false \ 89 | skia_use_libpng=true \ 90 | skia_use_system_libpng=true \ 91 | skia_use_zlib=true \ 92 | skia_use_system_zlib=true \ 93 | skia_use_libwebp=false \ 94 | skia_enable_pdf=true \ 95 | skia_use_sfntly=true \ 96 | skia_use_fontconfig=true \ 97 | skia_use_freetype=true \ 98 | skia_use_system_freetype2=true \ 99 | skia_enable_tools=false \ 100 | skia_use_lua=false \ 101 | skia_use_mesa=false \ 102 | skia_use_piex=false \ 103 | skia_use_dng_sdk=false \ 104 | " 105 | BUILD_COMMAND ninja -C ${SKIA_BUILD_DIR} -j1 106 | # there is no install step provided 107 | INSTALL_COMMAND true 108 | ) 109 | 110 | if (EXT_SKIA_ALWAYS_BUILD) 111 | # Make sure the target is always rebuilt. 112 | # Without this changing Skia sources doesn't trigger a ninja build. With this 113 | # ninja build is always triggered. This is not needed if you never touch the 114 | # Skia sources. Please note that enabling this ends up with re-building of 115 | # targets that depend on the library. :( 116 | ExternalProject_Add_Step(SKIA_build ForceBuild COMMAND true DEPENDERS build ALWAYS 1) 117 | endif () 118 | 119 | # taken from BUILD.gn (skia_public_includes, minus things that are obviously useless for us) 120 | set(SKIA_HEADERS 121 | ${SKIA_SRC}/include/c 122 | ${SKIA_SRC}/include/codec 123 | ${SKIA_SRC}/include/config 124 | ${SKIA_SRC}/include/core 125 | ${SKIA_SRC}/include/effects 126 | ${SKIA_SRC}/include/gpu 127 | ${SKIA_SRC}/include/gpu/gl 128 | ${SKIA_SRC}/include/pathops 129 | ${SKIA_SRC}/include/ports 130 | ${SKIA_SRC}/include/svg 131 | ${SKIA_SRC}/include/utils 132 | ) 133 | 134 | # this must match what BUILD.gn sets 135 | # if it's wrong it can result in all kinds of funny behavior 136 | set(SKIA_DEFINES 137 | "SK_SAMPLES_FOR_X" # always set for linux, even if there's no X used 138 | "SK_SUPPORT_GPU=1" # skia_enable_gpu 139 | #"SK_VULKAN" # skia_use_vulkan 140 | #"SK_ENABLE_VK_LAYERS" # skia_enable_vulkan_debug_layers 141 | #"SK_ENABLE_SPIRV_VALIDATION" # skia_enable_spirv_validation 142 | #"SK_HAS_JPEG_LIBRARY" # skia_use_libjpeg_turbo 143 | "SK_HAS_PNG_LIBRARY" # skia_use_libpng 144 | "SK_SUPPORT_PDF" # skia_enable_pdf 145 | "SK_PDF_USE_SFNTLY" # skia_use_sfntly 146 | #"SK_HAS_WEBP_LIBRARY" # skia_use_libwebp 147 | "SK_XML" # skia_use_expat 148 | ) 149 | 150 | if (SK_CONF_SHARED) 151 | liast(APPEND SKIA_DEFINES "SKIA_DLL") 152 | endif () 153 | 154 | # GN doesn't seem to do any fancy stuff with library dependencies - it just 155 | # asks the compiler to link to them w/o any fany search strategies. This 156 | # also means that whatever is found here is not guaranteed to be the same as 157 | # what GN finds. :-( 158 | # Anyway, using plain find_library() seems to be the next closest thing, 159 | # so even if some libraries provide pkg_config or special packages for CMake, 160 | # only find_library() is used here. 161 | # This is needed only for static library build where the dependencies have 162 | # to be added explicitly. 163 | if (NOT EXT_SKIA_SHARED) 164 | function(ADD_SKIA_LIBRARY_DEPENDENCY LIB_NAME_LIST) 165 | foreach(LIB_NAME ${LIB_NAME_LIST}) 166 | message(STATUS "Searching for ${LIB_NAME}...") 167 | find_library(LIB${LIB_NAME} ${LIB_NAME}) 168 | if (NOT LIB${LIB_NAME}) 169 | message(FATAL_ERROR "Can't find required library ${LIB_NAME}.") 170 | endif () 171 | set(SKIA_DEPENDENCIES "${SKIA_DEPENDENCIES};${LIB${LIB_NAME}}" PARENT_SCOPE) 172 | endforeach() 173 | endfunction() 174 | 175 | # seem to be always required... 176 | ADD_SKIA_LIBRARY_DEPENDENCY("dl") 177 | ADD_SKIA_LIBRARY_DEPENDENCY("pthread") 178 | 179 | # when skia_enable_gpu: 180 | #ADD_SKIA_LIBRARY_DEPENDENCY("EGL") # skia_use_egl 181 | ADD_SKIA_LIBRARY_DEPENDENCY("GL") # !skia_use_egl # TODO: GLU? 182 | 183 | ADD_SKIA_LIBRARY_DEPENDENCY("icuuc") # skia_use_system_icu 184 | ADD_SKIA_LIBRARY_DEPENDENCY("expat") #skia_use_system_expat 185 | #ADD_SKIA_LIBRARY_DEPENDENCY("jpeg") # skia_use_system_libjpeg_turbo 186 | ADD_SKIA_LIBRARY_DEPENDENCY("png") # skia_use_system_libpng 187 | ADD_SKIA_LIBRARY_DEPENDENCY(${EXT_SKIA_USE_SYSTEM_ZLIB} "z") # skia_use_system_zlib 188 | 189 | # webp integration doesn't expose the system option... 190 | #ADD_SKIA_LIBRARY_DEPENDENCY("webp") # SK_CONF_IS_OFFICIAL_BUILD && skia_use_libwebp 191 | 192 | ADD_SKIA_LIBRARY_DEPENDENCY(${EXT_SKIA_USE_FONTCONFIG} "fontconfig") # skia_use_fontconfig 193 | ADD_SKIA_LIBRARY_DEPENDENCY(${EXT_SKIA_USE_FREETYPE2} "freetype") # skia_use_system_freetype2 194 | endif (NOT EXT_SKIA_SHARED) 195 | 196 | if (EXT_SKIA_SHARED) 197 | add_library(SKIA SHARED IMPORTED GLOBAL) 198 | set(SKIA_LIBRARY "${SKIA_BUILD_DIR}/${CMAKE_SHARED_LIBRARY_PREFIX}skia${CMAKE_SHARED_LIBRARY_SUFFIX}") 199 | else (EXT_SKIA_SHARED) 200 | add_library(SKIA STATIC IMPORTED GLOBAL) 201 | set(SKIA_LIBRARY "${SKIA_BUILD_DIR}/${CMAKE_STATIC_LIBRARY_PREFIX}skia${CMAKE_STATIC_LIBRARY_SUFFIX}") 202 | endif (EXT_SKIA_SHARED) 203 | 204 | set_target_properties(SKIA PROPERTIES 205 | IMPORTED_LOCATION "${SKIA_LIBRARY}" 206 | INTERFACE_INCLUDE_DIRECTORIES "${SKIA_HEADERS}" 207 | INTERFACE_COMPILE_DEFINITIONS "${SKIA_DEFINES}" 208 | IMPORTED_LINK_INTERFACE_LIBRARIES "${SKIA_DEPENDENCIES}" 209 | ) 210 | add_dependencies(SKIA SKIA_build) 211 | -------------------------------------------------------------------------------- /ext/download-dependencies.sh: -------------------------------------------------------------------------------- 1 | #!/bin/bash 2 | set -e 3 | 4 | # change to the directory where the script is stored 5 | cd `dirname $0` 6 | 7 | if [ -e skia ]; then 8 | echo "Skipping Skia download because it's been downloaded already." 9 | else 10 | # TODO: use a fixed (verified-working) revision 11 | git clone https://skia.googlesource.com/skia.git 12 | ( 13 | cd skia 14 | tools/git-sync-deps 15 | ) 16 | fi 17 | -------------------------------------------------------------------------------- /src/CMakeLists.txt: -------------------------------------------------------------------------------- 1 | add_subdirectory(headless) 2 | add_subdirectory(qt) 3 | -------------------------------------------------------------------------------- /src/headless/CMakeLists.txt: -------------------------------------------------------------------------------- 1 | # Minimal headless skia example 2 | add_executable(skia_example_headless 3 | SkiaExampleHeadless.cpp 4 | ) 5 | target_link_libraries(skia_example_headless SKIA) 6 | -------------------------------------------------------------------------------- /src/headless/SkiaExampleHeadless.cpp: -------------------------------------------------------------------------------- 1 | /* 2 | * Copyright 2017 David Kozub 3 | * 4 | * This file is part of SkiaExample. 5 | * 6 | * SkiaExample is free software: you can redistribute it and/or modify 7 | * it under the terms of the GNU General Public License as published by 8 | * the Free Software Foundation, either version 3 of the License, or 9 | * (at your option) any later version. 10 | * 11 | * SkiaExample is distributed in the hope that it will be useful, 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 | * GNU General Public License for more details. 15 | * 16 | * You should have received a copy of the GNU General Public License 17 | * along with SkiaExample. If not, see . 18 | */ 19 | #include 20 | #include 21 | 22 | #include 23 | #include 24 | #include 25 | #include 26 | #include 27 | 28 | void raster(int width, int height, void (*draw)(SkCanvas&), const char* path) 29 | { 30 | sk_sp rasterSurface = SkSurface::MakeRasterN32Premul(width, height); 31 | if (!rasterSurface) 32 | throw std::runtime_error("can't create surface"); 33 | 34 | SkCanvas* rasterCanvas = rasterSurface->getCanvas(); 35 | if (!rasterCanvas) 36 | throw std::runtime_error("can't get canvas"); 37 | 38 | draw(*rasterCanvas); 39 | 40 | sk_sp img(rasterSurface->makeImageSnapshot()); 41 | if (!img) 42 | throw std::runtime_error("can't make image snapshot"); 43 | 44 | sk_sp png(img->encode()); 45 | if (!png) 46 | throw std::runtime_error("can't encode png"); 47 | 48 | SkFILEWStream out(path); 49 | out.write(png->data(), png->size()); 50 | } 51 | 52 | void drawTest(SkCanvas &canvas) 53 | { 54 | canvas.clear(SK_ColorWHITE); 55 | 56 | SkPaint paint; 57 | paint.setTextSize(32.0f); 58 | paint.setAntiAlias(true); 59 | paint.setColor(SK_ColorBLACK); 60 | paint.setStyle(SkPaint::kFill_Style); 61 | canvas.drawString("Skia Test", 20, 32, paint); 62 | } 63 | 64 | int main() 65 | { 66 | const char *testFileName = "test.png"; 67 | const int WIDTH = 100; 68 | const int HEIGHT = 100; 69 | 70 | std::cout << "Writing test output to " << testFileName << std::endl; 71 | raster(WIDTH, HEIGHT, drawTest, testFileName); 72 | } 73 | -------------------------------------------------------------------------------- /src/qt/CMakeLists.txt: -------------------------------------------------------------------------------- 1 | # Skia example with Qt GUI 2 | # inspired by http://doc.qt.io/qt-5/cmake-manual.html 3 | 4 | # Find includes in corresponding build directories 5 | set(CMAKE_INCLUDE_CURRENT_DIR ON) 6 | # Instruct CMake to run moc automatically when needed. 7 | set(CMAKE_AUTOMOC ON) 8 | 9 | # Find the QtWidgets library 10 | find_package(Qt5Widgets REQUIRED) 11 | 12 | add_executable(skia_example_qt 13 | SkiaPolygonWidget.h 14 | SkiaPolygonWidget.cpp 15 | SkiaExampleQt.cpp 16 | ) 17 | target_link_libraries(skia_example_qt SKIA Qt5::Widgets) 18 | -------------------------------------------------------------------------------- /src/qt/SkiaExampleQt.cpp: -------------------------------------------------------------------------------- 1 | /* 2 | * Copyright 2017 David Kozub 3 | * 4 | * This file is part of SkiaExample. 5 | * 6 | * SkiaExample is free software: you can redistribute it and/or modify 7 | * it under the terms of the GNU General Public License as published by 8 | * the Free Software Foundation, either version 3 of the License, or 9 | * (at your option) any later version. 10 | * 11 | * SkiaExample is distributed in the hope that it will be useful, 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 | * GNU General Public License for more details. 15 | * 16 | * You should have received a copy of the GNU General Public License 17 | * along with SkiaExample. If not, see . 18 | */ 19 | #include 20 | #include 21 | #include 22 | #include 23 | #include 24 | #include 25 | 26 | #include "SkiaPolygonWidget.h" 27 | 28 | class SkiaExampleQt: public QWidget 29 | { 30 | Q_OBJECT 31 | 32 | public: 33 | explicit SkiaExampleQt(QWidget *parent = nullptr): 34 | QWidget(parent) 35 | { 36 | setWindowTitle(QString::fromUtf8(u8"Qt Skia Example")); 37 | 38 | QVBoxLayout * vboxLayout(new QVBoxLayout); 39 | 40 | m_skiaPolygonWidget = new SkiaPolygonWidget(this); 41 | vboxLayout->addWidget(m_skiaPolygonWidget, 1); 42 | m_skiaPolygonWidget->show(); 43 | 44 | QFormLayout * formLayout(new QFormLayout); 45 | 46 | QSpinBox * vertexCountSpinBox(new QSpinBox); 47 | vertexCountSpinBox->setRange(3, 20); 48 | vertexCountSpinBox->setSingleStep(1); 49 | vertexCountSpinBox->setValue(m_skiaPolygonWidget->vertexCount()); 50 | 51 | formLayout->addRow(u8"&Vertices", vertexCountSpinBox); 52 | 53 | QSlider * angleSlider(new QSlider); 54 | angleSlider->setOrientation(Qt::Horizontal); 55 | angleSlider->setRange(0, 359); 56 | formLayout->addRow(u8"&Rotation", angleSlider); 57 | 58 | vboxLayout->addLayout(formLayout); 59 | 60 | setLayout(vboxLayout); 61 | 62 | // there is valueChanget(int) and valueChanged(const QString&), use static_cast to pick the int one 63 | connect(vertexCountSpinBox, static_cast(&QSpinBox::valueChanged), 64 | m_skiaPolygonWidget, &SkiaPolygonWidget::setVertexCount); 65 | connect(angleSlider, &QSlider::valueChanged, [this](int angleDegrees) 66 | { 67 | m_skiaPolygonWidget->setAngle(angleDegrees * M_PI/180); 68 | }); 69 | } 70 | 71 | private: 72 | SkiaPolygonWidget * m_skiaPolygonWidget; 73 | }; 74 | 75 | int main(int argc, char *argv[]) 76 | { 77 | QApplication a(argc, argv); 78 | 79 | SkiaExampleQt w; 80 | w.show(); 81 | 82 | return a.exec(); 83 | } 84 | 85 | #include "SkiaExampleQt.moc" 86 | -------------------------------------------------------------------------------- /src/qt/SkiaPolygonWidget.cpp: -------------------------------------------------------------------------------- 1 | /* 2 | * Copyright 2017 David Kozub 3 | * 4 | * This file is part of SkiaExample. 5 | * 6 | * SkiaExample is free software: you can redistribute it and/or modify 7 | * it under the terms of the GNU General Public License as published by 8 | * the Free Software Foundation, either version 3 of the License, or 9 | * (at your option) any later version. 10 | * 11 | * SkiaExample is distributed in the hope that it will be useful, 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 | * GNU General Public License for more details. 15 | * 16 | * You should have received a copy of the GNU General Public License 17 | * along with SkiaExample. If not, see . 18 | */ 19 | #include "SkiaPolygonWidget.h" 20 | 21 | #include 22 | #include 23 | #include 24 | 25 | #include 26 | #include 27 | #include 28 | #include 29 | 30 | #include 31 | #include 32 | #include 33 | #include 34 | #include 35 | 36 | /** 37 | * Skia and Qt use different style of naming pixel formats. 38 | * 39 | * Qt's Format_ARGB32 means a pixel loaded into a 32bit variable has the structure 40 | * 0xAARRGGBB. When stored in memory this becomes either BB, GG, RR, AA (little endian) 41 | * or AA, RR, GG, BB (big endian). 42 | * Then there is Format_RGBA8888 which is defined to be stored as RR, GG, BB, AA. In a 43 | * 32bit variable this becomes either 0xAABBGGRR (little endian) or 0xRRGGBBAA (big endian). 44 | * 45 | * Skia seems to label formats based on how the components are stored in memory: 46 | * kRGBA_8888_SkColorType means a pixel is stored in memory like this: 47 | * RR, GG, BB, AA. When loaded into a register this becomes either 0xAABBGGRR (little endian) 48 | * or 0xRRGGBBAA (big endian). 49 | * 50 | * This means that: 51 | * * for little endian: 52 | * kBGRA_8888_SkColorType (Skia) is the same as Format_ARGB32 (Qt) 53 | * kRGBA_8888_SkColorType (Skia) is the same as Format_RGBA8888 (Qt) 54 | * 55 | * * for big endian: 56 | * kBGRA_8888_SkColorType (Skia) would be Format_BGRA32 or Format_BGRA888 in Qt (but there's no such thing) 57 | * kRGBA_8888_SkColorType (Skia) is Format_RGBA888 (Qt) 58 | * 59 | * And, of course, Skia probably would not work on big endian even though there is some 60 | * half-baked support for big endian. 61 | */ 62 | 63 | #ifdef SK_CPU_BENDIAN 64 | // It seems that big endian is not even properly supported by Skia. 65 | // The mapping of Skia to Qt pixel formats would need to be extended here. 66 | #error Big endian not supported. 67 | #endif 68 | 69 | namespace 70 | { 71 | /** 72 | * Map a Skia color type a QImage premultiplied format. 73 | */ 74 | template 75 | struct SkColorTypeToQtFormatPreMultiplied; 76 | 77 | template<> 78 | struct SkColorTypeToQtFormatPreMultiplied 79 | { 80 | static constexpr QImage::Format value = QImage::Format_ARGB32_Premultiplied; 81 | }; 82 | 83 | template<> 84 | struct SkColorTypeToQtFormatPreMultiplied 85 | { 86 | static constexpr QImage::Format value = QImage::Format_RGBA8888_Premultiplied; 87 | }; 88 | 89 | SkColor skColorFromQColor(const QColor & qColor) 90 | { 91 | return SkColorSetARGB(qColor.alpha(), qColor.red(), qColor.green(), qColor.blue()); 92 | } 93 | 94 | constexpr QSize SIZE_HINT(400, 400); 95 | constexpr QSize MINIMUM_SIZE_HINT(200, 200); 96 | constexpr float DEFAULT_ANGLE = 0; 97 | constexpr unsigned DEFAULT_VERTEX_COUNT = 5; 98 | const QColor DEFAULT_BACKGROUND_COLOR(255, 255, 255, 255); 99 | const QColor DEFAULT_STROKE_COLOR(0, 0, 0, 255); 100 | const QColor DEFAULT_FILL_COLOR(0, 255, 0, 255); 101 | const QColor DEFAULT_TEXT_COLOR(0, 0, 0, 128); 102 | } 103 | 104 | SkiaPolygonWidget::SkiaPolygonWidget(QWidget *parent): 105 | QWidget(parent), 106 | m_angle(DEFAULT_ANGLE), 107 | m_vertexCount(DEFAULT_VERTEX_COUNT), 108 | m_backgroundColor(DEFAULT_BACKGROUND_COLOR), 109 | m_strokeColor(DEFAULT_STROKE_COLOR), 110 | m_textColor(DEFAULT_TEXT_COLOR), 111 | m_fillColor(DEFAULT_FILL_COLOR) 112 | { 113 | setSizePolicy(QSizePolicy::MinimumExpanding, QSizePolicy::MinimumExpanding); 114 | } 115 | 116 | QSize SkiaPolygonWidget::sizeHint() const 117 | { 118 | return SIZE_HINT; 119 | } 120 | 121 | QSize SkiaPolygonWidget::minimumSizeHint() const 122 | { 123 | return MINIMUM_SIZE_HINT; 124 | } 125 | 126 | void SkiaPolygonWidget::resizeEvent(QResizeEvent *event) 127 | { 128 | int size = std::min(width(), height()); 129 | 130 | if (size > 0) 131 | { 132 | /* 133 | * It would be ideal to use kBGRA_8888_SkColorType pixel format for the Skia 134 | * surface and QImage::Format_ARGB32_Premultiplied for the QImage format. 135 | * But Skia's 32bit backend always suppors exactly one of kBGRA_8888_SkColorType 136 | * and kRGBA_8888_SkColorType. There is kN32_SkColorType which then equals 137 | * to the selected one. So asking for kBGRA_8888_SkColorType here would 138 | * mean on some platforms (Windows?) the creation of the raster image would fail. 139 | * 140 | * For Linux kN32_SkColorType is forced (via SK_SAMPLES_FOR_X in SkUserConfig.h) 141 | * to kBGRA_8888_SkColorType. On Windows it seems to be equal to kRGBA_8888_SkColorType. 142 | * 143 | * If needed this could be changed in Skia configuration. 144 | */ 145 | m_skiaSurface = SkSurface::MakeRasterN32Premul(size, size); 146 | if (!m_skiaSurface) 147 | throw std::runtime_error("can't create Skia surface"); 148 | } 149 | else 150 | m_skiaSurface.reset(); 151 | 152 | QWidget::resizeEvent(event); 153 | } 154 | 155 | void SkiaPolygonWidget::paintEvent(QPaintEvent *) 156 | { 157 | QPainter painter(this); 158 | 159 | bool succeeded = false; 160 | if (m_skiaSurface) 161 | { 162 | SkCanvas* skiaCanvas = m_skiaSurface->getCanvas(); 163 | if (!skiaCanvas) 164 | throw std::runtime_error("cant' get Skia canvas"); 165 | 166 | render(*skiaCanvas); 167 | 168 | SkPixmap skiaPixmap; 169 | if (m_skiaSurface->peekPixels(&skiaPixmap)) 170 | { 171 | QImage qtImage(reinterpret_cast(skiaPixmap.addr()), 172 | skiaPixmap.width(), 173 | skiaPixmap.height(), 174 | skiaPixmap.rowBytes(), 175 | SkColorTypeToQtFormatPreMultiplied::value); 176 | 177 | // draw image centered, avoid skewing it 178 | const int imageWidth = skiaCanvas->getBaseLayerSize().width(); 179 | const int imageHeight = skiaCanvas->getBaseLayerSize().height(); 180 | const QRect content = contentsRect(); 181 | 182 | const int midX = content.x() + content.width()/2; 183 | const int midY = content.y() + content.height()/2; 184 | const int x = midX - imageWidth/2; 185 | const int y = midY - imageHeight/2; 186 | 187 | QRect drawRect(x, y, imageWidth, imageHeight); 188 | painter.drawImage(drawRect, qtImage); 189 | 190 | succeeded = true; 191 | } 192 | } 193 | 194 | if (!succeeded) 195 | painter.fillRect(contentsRect(), QColor(255, 0, 0)); 196 | } 197 | 198 | SkPath SkiaPolygonWidget::createPolygonPath(SkScalar size, SkScalar rotationAngle, unsigned count) 199 | { 200 | // draw the polygon as if it's in [-1,1]² 201 | SkPath path; 202 | path.moveTo(1, 0); 203 | const SkScalar angleStep = 2 * M_PI / count; 204 | for (int i = 0; i < count; i++) 205 | { 206 | const SkScalar a = angleStep * i; 207 | path.lineTo(std::cos(a), std::sin(a)); 208 | } 209 | 210 | // close the path 211 | path.lineTo(path.getPoint(0)); 212 | 213 | // rotate, shift (0,0) to the center and scale 214 | SkMatrix t; 215 | t.setRotate(rotationAngle * 180/M_PI); // radians to degrees 216 | t.postTranslate(1, 1); 217 | t.postScale(size/2, size/2); 218 | path.transform(t); 219 | return path; 220 | } 221 | 222 | void SkiaPolygonWidget::render(SkCanvas &canvas) 223 | { 224 | canvas.clear(skColorFromQColor(m_backgroundColor)); 225 | 226 | SkPath path(createPolygonPath(canvas.getBaseLayerSize().width(), m_angle, m_vertexCount)); 227 | 228 | SkPaint paint; 229 | paint.setAntiAlias(true); 230 | 231 | // fill 232 | paint.setStyle(SkPaint::kFill_Style); 233 | paint.setColor(skColorFromQColor(m_fillColor)); 234 | canvas.drawPath(path, paint); 235 | 236 | // stroke 237 | paint.setStyle(SkPaint::kStroke_Style); 238 | paint.setStrokeWidth(2.0f); 239 | paint.setColor(skColorFromQColor(m_strokeColor)); 240 | canvas.drawPath(path, paint); 241 | 242 | paint.setTextSize(32.0f); 243 | paint.setColor(skColorFromQColor(m_textColor)); 244 | paint.setStyle(SkPaint::kFill_Style); 245 | canvas.drawString(std::to_string(m_vertexCount).c_str(), 0, canvas.getBaseLayerSize().height(), paint); 246 | } 247 | 248 | #include "SkiaPolygonWidget.moc" 249 | -------------------------------------------------------------------------------- /src/qt/SkiaPolygonWidget.h: -------------------------------------------------------------------------------- 1 | /* 2 | * Copyright 2017 David Kozub 3 | * 4 | * This file is part of SkiaExample. 5 | * 6 | * SkiaExample is free software: you can redistribute it and/or modify 7 | * it under the terms of the GNU General Public License as published by 8 | * the Free Software Foundation, either version 3 of the License, or 9 | * (at your option) any later version. 10 | * 11 | * SkiaExample is distributed in the hope that it will be useful, 12 | * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 | * GNU General Public License for more details. 15 | * 16 | * You should have received a copy of the GNU General Public License 17 | * along with SkiaExample. If not, see . 18 | */ 19 | #ifndef SKIA_POLYGON_WIDGET_H 20 | #define SKIA_POLYGON_WIDGET_H 21 | 22 | #include 23 | 24 | #include 25 | #include "SkSurface.h" 26 | 27 | // this is inspired by skia/debugger/SkRasterWidget.cpp 28 | class SkiaPolygonWidget: public QWidget 29 | { 30 | Q_OBJECT 31 | Q_PROPERTY(float angle READ angle WRITE setAngle NOTIFY angleChanged) 32 | Q_PROPERTY(unsigned vertexCount READ vertexCount WRITE setVertexCount NOTIFY vertexCountChanged) 33 | Q_PROPERTY(QColor backgroundColor READ backgroundColor WRITE setBackgroundColor NOTIFY backgroundColorChanged) 34 | Q_PROPERTY(QColor strokeColor READ strokeColor WRITE setStrokeColor NOTIFY strokeColorChanged) 35 | Q_PROPERTY(QColor fillColor READ fillColor WRITE setFillColor NOTIFY fillColorChanged) 36 | Q_PROPERTY(QColor textColor READ textColor WRITE setTextColor NOTIFY textColorChanged) 37 | 38 | public: 39 | SkiaPolygonWidget(QWidget *parent = nullptr); 40 | 41 | virtual QSize sizeHint() const override; 42 | virtual QSize minimumSizeHint() const override; 43 | 44 | void setAngle(float a) 45 | { 46 | m_angle = a; 47 | update(); 48 | emit angleChanged(a); 49 | } 50 | 51 | float angle() const 52 | { 53 | return m_angle; 54 | } 55 | 56 | void setVertexCount(unsigned n) 57 | { 58 | m_vertexCount = n; 59 | update(); 60 | emit vertexCountChanged(n); 61 | } 62 | 63 | unsigned vertexCount() const 64 | { 65 | return m_vertexCount; 66 | } 67 | 68 | void setBackgroundColor(const QColor &c) 69 | { 70 | m_backgroundColor = c; 71 | update(); 72 | emit backgroundColorChanged(c); 73 | } 74 | 75 | const QColor& backgroundColor() const 76 | { 77 | return m_backgroundColor; 78 | } 79 | 80 | void setStrokeColor(const QColor &c) 81 | { 82 | m_strokeColor = c; 83 | update(); 84 | emit strokeColorChanged(c); 85 | } 86 | 87 | const QColor& strokeColor() const 88 | { 89 | return m_strokeColor; 90 | } 91 | 92 | void setFillColor(const QColor &c) 93 | { 94 | m_fillColor = c; 95 | update(); 96 | emit fillColorChanged(c); 97 | } 98 | 99 | const QColor& fillColor() const 100 | { 101 | return m_fillColor; 102 | } 103 | 104 | void setTextColor(const QColor &c) 105 | { 106 | m_textColor = c; 107 | update(); 108 | emit textColorChanged(c); 109 | } 110 | 111 | const QColor& textColor() const 112 | { 113 | return m_textColor; 114 | } 115 | 116 | signals: 117 | void angleChanged(float); 118 | void vertexCountChanged(unsigned); 119 | void backgroundColorChanged(QColor); 120 | void strokeColorChanged(QColor); 121 | void fillColorChanged(QColor); 122 | void textColorChanged(QColor); 123 | 124 | protected: 125 | virtual void resizeEvent(QResizeEvent *event) override; 126 | virtual void paintEvent(QPaintEvent *event) override; 127 | 128 | private: 129 | static SkPath createPolygonPath(SkScalar size, SkScalar rotationAngle, unsigned count); 130 | void render(SkCanvas &canvas); 131 | 132 | float m_angle; 133 | unsigned m_vertexCount; 134 | QColor m_backgroundColor; 135 | QColor m_strokeColor; 136 | QColor m_fillColor; 137 | QColor m_textColor; 138 | sk_sp m_skiaSurface; 139 | }; 140 | 141 | #endif // SKIA_POLYGON_WIDGET_H 142 | --------------------------------------------------------------------------------