在PPAPI插件中使用Skia绘图

[**Windows下从源码编译Skia**](http://blog.csdn.net/foruok/article/details/50524726)一文介绍了Skia的编译，现在我们可以尝试在PPAPI插件中来使用Skia了。 > foruok原创，如需转载请关注foruok的微信订阅号“程序视界”联系foruok。 # Skia的关键类库官网[https://skia.org/](https://skia.org/)上有文档，可以看。然后下载的源码，可以使用SourceInsight之类的工具来查看。具体不再细说，我这里只提用到的三个关键类： - [SkPaint](https://skia.org/user/api/skpaint) - [SkCanvas](https://skia.org/user/api/skcanvas) - SkBitmap SkCanvas是画布，你可以在它上面画任意的图元，比如矩形、圆型、文字、弧…… SkPaint则是工具箱，聚合了画笔、颜色等各种绘画时要用的配置选项。 SkBitmap代表了一块图像数据。你调用SkCanvas的方法绘制图元，这些图元对应的数据一定要有个地方保存或显示，用于保存或显示图像数据的那个角色，被称为backends。SkCanvas的backends，有好几种，我们这个简单的示例ppapi_skia只用到了SkBitmap这种后端。 2D绘图类库的基本设计都差不多，我的《[**Qt on Android核心编程**](http://item.jd.com/11571639.html)》一书里对Qt绘图有介绍，两厢比对，就会发现设计得差不多。不过有一点不同，QPainter会保存你设置的绘图选项（颜色、画笔等），而SkCanvas则不会，需要自己设计数据结构和逻辑来保存。 # ppapi_skia项目 ppapi_skia项目基于ppapi_simple而来，请先参考[**PPAPI插件的绘图与输入事件处理**](http://blog.csdn.net/foruok/article/details/50499813)这篇文章。不过为了方便调用Skia（C++类库），我这次用了cpp源文件，ppapi_skia.cpp。（吐槽下，VS2013对于C文件的即时提示太弱……）我还改了ppapi_simple，使用了FlushCompletionCallback来优化绘图流程。 Skia默认编译出来的是静态库，对于一个简单的PPAPI+Skia插件，我不知道需要链接哪些lib，写好了代码，编译，根据undefined reference错误一通狂找，发现要链接下列lib： ~~~ skia_core.lib skia_ports.lib skia_utils.lib skia_effects.lib skia_skgpu.lib skia_opts.lib skia_opts_ssse3.lib skia_opts_sse41.lib skia_opts_avx.lib skia_images.lib skia_sfnt.lib libetc1.lib libSkKTX.lib opengl32.lib ~~~ [**Windows下从源码编译Skia**](http://blog.csdn.net/foruok/article/details/50524726)一文提到编译后的lib文件路径是：E:\sources\skia\out\Release。设置到项目的附加库目录列表中。skia还依赖其他一些库文件，在E:\sources\skia\out\Release\obj\gyp目录下，把这个目录添加到附加库目录列表里。 Skia需要OpenGL，我们得链接Opengl32.lib，Windows SDK里有。 skia编译时加了/MD参数，CEF编译时用的MT，如果你用PPAPI的C++接口，就会冲突了。要么改skia，要么改CEF。skia库小，改它吧。我还没找到怎么在生成构建文件时设置，最简单直接的，就是到E:\sources\skia\out\Release\obj\gyp这里，把*.ninja文件里的/MD都修改为/MT。然后重新编译。如过用C接口，没关系，把PPAPI的代码生成选项里的运行库修改为MD即可。我偷懒，就用C接口，把ppapi_skia项目的运行库选项设置为了MD。好，关于工程基本就这样了。 # 源码分C++源码和HTML源码。 ### C++代码 So，源码来了，基于C代码改过来，有点乱，不过可以说明用法。 ~~~ /* * Copyright (c) 2016 foruok@程序视界. All rights reserved. * 2016-1-16, edited by foruok. * 如需转载，请关注微信订阅号“程序视界”，回复foruok获取其联系方式 */ #include <stdint.h> #include <stdlib.h> #include <string.h> #include <Windows.h> #include <tchar.h> #include "ppapi/c/pp_completion_callback.h" #include "ppapi/c/pp_errors.h" #include "ppapi/c/pp_instance.h" #include "ppapi/c/pp_module.h" #include "ppapi/c/pp_rect.h" #include "ppapi/c/pp_var.h" #include "ppapi/c/ppb.h" #include "ppapi/c/ppb_core.h" #include "ppapi/c/ppb_graphics_2d.h" #include "ppapi/c/ppb_image_data.h" #include "ppapi/c/ppb_instance.h" #include "ppapi/c/ppb_view.h" #include "ppapi/c/ppp.h" #include "ppapi/c/ppp_instance.h" #include "ppapi/c/ppb_input_event.h" #include "ppapi/c/ppp_input_event.h" #include "SkPaint.h" #include "SkBitmap.h" #include "SkCanvas.h" PPB_GetInterface g_get_browser_interface = NULL; const PPB_Core* g_core_interface; const PPB_Graphics2D* g_graphics_2d_interface; const PPB_ImageData* g_image_data_interface; const PPB_Instance* g_instance_interface; const PPB_View* g_view_interface; const PPB_InputEvent *g_input_interface; const PPB_MouseInputEvent *g_mouse_interface; /* PPP_Instance implementation -----------------------------------------------*/ struct InstanceInfo { PP_Instance pp_instance; struct PP_Size last_size; PP_Resource graphics; PP_Resource image; SkBitmap *bitmap; SkCanvas *canvas; int inFlush; int requestPaint; unsigned int colorIndex; struct InstanceInfo* next; }; /** Linked list of all live instances. */ struct InstanceInfo* all_instances = NULL; /** Returns a refed resource corresponding to the created graphics 2d. */ PP_Resource MakeAndBindGraphics2D(PP_Instance instance, const struct PP_Size* size) { PP_Resource graphics; graphics = g_graphics_2d_interface->Create(instance, size, PP_FALSE); if (!graphics) return 0; if (!g_instance_interface->BindGraphics(instance, graphics)) { g_core_interface->ReleaseResource(graphics); return 0; } return graphics; } unsigned int g_colors[4] = { 0xFF0000FF, 0xFFFF00FF, 0xFF00FFFF, 0xFFEA00FF }; void DoPaint(struct InstanceInfo * instance); void FlushCompletionCallback(void* user_data, int32_t result) { struct InstanceInfo *inst = (struct InstanceInfo*)user_data; inst->inFlush = 0; if (inst->requestPaint) { inst->requestPaint = 0; DoPaint(inst); } } const char szHelloSkia[] = "Hello Skia in PPAPI"; void DoPaint(struct InstanceInfo * instance) { instance->inFlush = 1; instance->colorIndex++; if (instance->colorIndex >= sizeof(g_colors) / sizeof(g_colors[0])) instance->colorIndex = 0; /* [2] Skia Paint * foruok */ instance->canvas->drawColor(g_colors[instance->colorIndex]); SkPaint paint; paint.setColor(SK_ColorWHITE); paint.setAntiAlias(true); paint.setLCDRenderText(true); paint.setStrokeWidth(4); instance->canvas->drawText(szHelloSkia, ARRAYSIZE(szHelloSkia) - 1, 20.0f, 20.0f, paint); paint.setColor(0x80CCCCCC); instance->canvas->drawCircle(150, 130, 100, paint); /* Paint image to graphics 2d. */ g_graphics_2d_interface->ReplaceContents(instance->graphics, instance->image); g_graphics_2d_interface->Flush(instance->graphics, PP_MakeCompletionCallback(&FlushCompletionCallback, instance)); } void Repaint(struct InstanceInfo* instance, const struct PP_Size* size) { /* Ensure the graphics 2d is ready. */ if (!instance->graphics) { instance->graphics = MakeAndBindGraphics2D(instance->pp_instance, size); if (!instance->graphics) return; } /* Create image data to paint into. */ if (!instance->image) { instance->image = g_image_data_interface->Create( instance->pp_instance, PP_IMAGEDATAFORMAT_BGRA_PREMUL, size, PP_TRUE); if (!instance->image) return; } /* [1] setup SkCanvas's backends * foruok */ if (!instance->bitmap) { /* foruok * get image data from PPB interfaces */ struct PP_ImageDataDesc image_desc; uint32_t* image_data; g_image_data_interface->Describe(instance->image, &image_desc); image_data = (uint32_t*)g_image_data_interface->Map(instance->image); if (!image_data) { g_core_interface->ReleaseResource(instance->image); return; } /* foruok * bind PPAPI image data to SkBitmap */ SkImageInfo ii = SkImageInfo::Make(size->width, size->height, kBGRA_8888_SkColorType, kPremul_SkAlphaType, kLinear_SkColorProfileType); instance->bitmap = new SkBitmap(); instance->bitmap->installPixels(ii, image_data, image_desc.stride); if (!instance->canvas) { /* foruok * construct SkCanvas with SkBitmap backend */ instance->canvas = new SkCanvas(*instance->bitmap); } } if (!instance->inFlush) { DoPaint(instance); } else { instance->requestPaint = 1; } } /** Returns the info for the given instance, or NULL if it's not found. */ struct InstanceInfo* FindInstance(PP_Instance instance) { struct InstanceInfo* cur = all_instances; while (cur) { if (cur->pp_instance == instance) return cur; cur = cur->next; } return NULL; } PP_Bool Instance_DidCreate(PP_Instance instance, uint32_t argc, const char* argn[], const char* argv[]) { struct InstanceInfo* info = (struct InstanceInfo*)calloc(1, sizeof(struct InstanceInfo)); info->pp_instance = instance; /* Insert into linked list of live instances. */ info->next = all_instances; all_instances = info; g_input_interface->RequestInputEvents(instance, PP_INPUTEVENT_CLASS_MOUSE); g_input_interface->RequestFilteringInputEvents(instance, PP_INPUTEVENT_CLASS_MOUSE); OutputDebugString(_T("Instance_DidCreate\r\n")); return PP_TRUE; } void Instance_DidDestroy(PP_Instance instance) { /* Find the matching item in the linked list, delete it, and patch the * links. */ struct InstanceInfo** prev_ptr = &all_instances; struct InstanceInfo* cur = all_instances; while (cur) { if (instance == cur->pp_instance) { *prev_ptr = cur->next; g_core_interface->ReleaseResource(cur->graphics); free(cur); return; } prev_ptr = &cur->next; cur = cur->next; } } void Instance_DidChangeView(PP_Instance pp_instance, PP_Resource view) { struct PP_Rect position; struct InstanceInfo* info = FindInstance(pp_instance); if (!info) return; if (g_view_interface->GetRect(view, &position) == PP_FALSE) return; if (info->last_size.width != position.size.width || info->last_size.height != position.size.height) { /* Got a resize, repaint the plugin. */ Repaint(info, &position.size); info->last_size.width = position.size.width; info->last_size.height = position.size.height; } OutputDebugString(_T("Instance_DidChangeView\r\n")); } void Instance_DidChangeFocus(PP_Instance pp_instance, PP_Bool has_focus) { } PP_Bool Instance_HandleDocumentLoad(PP_Instance pp_instance, PP_Resource pp_url_loader) { return PP_FALSE; } static PPP_Instance instance_interface = { &Instance_DidCreate, &Instance_DidDestroy, &Instance_DidChangeView, &Instance_DidChangeFocus, &Instance_HandleDocumentLoad }; PP_Bool InputEvent_HandleInputEvent(PP_Instance instance, PP_Resource input_event) { struct PP_Point pt; TCHAR szLog[512] = { 0 }; switch (g_input_interface->GetType(input_event)) { case PP_INPUTEVENT_TYPE_MOUSEDOWN: pt = g_mouse_interface->GetPosition(input_event); _stprintf_s(szLog, 512, _T("InputEvent_HandleInputEvent, mouse down at [%d, %d]\r\n"), pt.x, pt.y); OutputDebugString(szLog); break; /* case PP_INPUTEVENT_TYPE_MOUSEUP: OutputDebugString(_T("InputEvent_HandleInputEvent, mouse up\r\n")); break; case PP_INPUTEVENT_TYPE_MOUSEMOVE: OutputDebugString(_T("InputEvent_HandleInputEvent, mouse move\r\n")); break; case PP_INPUTEVENT_TYPE_MOUSEENTER: OutputDebugString(_T("InputEvent_HandleInputEvent, mouse enter\r\n")); break; case PP_INPUTEVENT_TYPE_MOUSELEAVE: OutputDebugString(_T("InputEvent_HandleInputEvent, mouse leave\r\n")); break; */ default: return PP_FALSE; } struct InstanceInfo* info = FindInstance(instance); if (info && info->last_size.width > 0) { Repaint(info, &info->last_size); } return PP_TRUE; } static PPP_InputEvent input_interface = { &InputEvent_HandleInputEvent }; /* Global entrypoints --------------------------------------------------------*/ PP_EXPORT int32_t PPP_InitializeModule(PP_Module module, PPB_GetInterface get_browser_interface) { g_get_browser_interface = get_browser_interface; g_core_interface = (const PPB_Core*) get_browser_interface(PPB_CORE_INTERFACE); g_instance_interface = (const PPB_Instance*) get_browser_interface(PPB_INSTANCE_INTERFACE); g_image_data_interface = (const PPB_ImageData*) get_browser_interface(PPB_IMAGEDATA_INTERFACE); g_graphics_2d_interface = (const PPB_Graphics2D*) get_browser_interface(PPB_GRAPHICS_2D_INTERFACE); g_view_interface = (const PPB_View*) get_browser_interface(PPB_VIEW_INTERFACE); g_input_interface = (const PPB_InputEvent*)get_browser_interface(PPB_INPUT_EVENT_INTERFACE); g_mouse_interface = (const PPB_MouseInputEvent*)get_browser_interface(PPB_MOUSE_INPUT_EVENT_INTERFACE); if (!g_core_interface || !g_instance_interface || !g_image_data_interface || !g_graphics_2d_interface || !g_view_interface || !g_input_interface || !g_mouse_interface) return -1; OutputDebugString(_T("PPP_InitializeModule\r\n")); return PP_OK; } PP_EXPORT void PPP_ShutdownModule() { } PP_EXPORT const void* PPP_GetInterface(const char* interface_name) { if (strcmp(interface_name, PPP_INSTANCE_INTERFACE) == 0) { OutputDebugString(_T("PPP_GetInterface, instance_interface\r\n")); return &instance_interface; } else if (strcmp(interface_name, PPP_INPUT_EVENT_INTERFACE) == 0) { OutputDebugString(_T("PPP_GetInterface, input_interface\r\n")); return &input_interface; } return NULL; } ~~~ 上面代码里我标注了两处与Skia有关的改动，[1]和[2]，也加了注释。另外就是使用FlushCompletionCallback来处理绘图和刷新，把ppapi_simple中的一些全局变量修改为与插件实例对象绑定的变量，这样可以支持一个网页里嵌入多个plugin了。 ### HTML代码 ppapi_skia.html代码如下： ~~~ <!DOCTYPE html> <html>  <head> <title>PPAPI-SKIA</title> </head> <body> <embed id="plugin" type="application/x-ppapi-skia" width="400px" height="300px"> </body> </html> ~~~ ### 运行效果使用下面命令来运行： ~~~ cefsimple.exe --ppapi-out-of-process --register-pepper-plugins="E:\sources\CEF\2526\chromium\src\cef\binary_distrib\cef_binary_3.2526.1364.gf6bf57b_windows32\Release\ppapi_skia.dll;application/x-ppapi-skia" --url=file:///E:/sources/CEF/2526/chromium/src/cef/binary_distrib/cef_binary_3.2526.1364.gf6bf57b_windows32/Release/ppapi_skia.html ~~~ 效果如下： ![PPAPI-Skia](https://docs.gechiui.com/gc-content/uploads/sites/kancloud/2016-02-22_56caac346903b.jpg "") Ok，这个示例就这么着了。有时间我会用Skia+PPAPI的方式制作一个简单的涂鸦板插件。其他参考文章： - [**CEF Windows开发环境搭建**](http://blog.csdn.net/foruok/article/details/50468642) - [**CEF加载PPAPI插件**](http://blog.csdn.net/foruok/article/details/50485448) - [**VS2013编译最简单的PPAPI插件**](http://blog.csdn.net/foruok/article/details/50485461) - [**理解PPAPI的设计**](http://blog.csdn.net/foruok/article/details/50486788) - [**PPAPI插件与浏览器的交互过程**](http://blog.csdn.net/foruok/article/details/50494061) - [**Windows下从源码编译CEF**](http://blog.csdn.net/foruok/article/details/50498740) - [**编译PPAPI的media_stream_video示例**](http://blog.csdn.net/foruok/article/details/50498873) - [**PPAPI插件的绘图与输入事件处理**](http://blog.csdn.net/foruok/article/details/50499813) - [**在PPAPI插件中创建本地窗口**](http://blog.csdn.net/foruok/article/details/50513228) - [**PPAPI插件与浏览器的通信**](http://blog.csdn.net/foruok/article/details/50513315) - [**Windows下从源码编译Skia**](http://blog.csdn.net/foruok/article/details/50524726)