问题描述
寻找正确的方法来调整Emscripten的SDL2窗口/画布的大小。 目前,我正在JS'resize'事件上添加事件侦听器,并将Canvas父级的客户端宽度+高度发送给Emscripten,然后更新在每个渲染器上调用的width和height变量。
这将产生奇怪的结果-刻度始终处于关闭状态,实际可用的SDL2区域未更改,并且指针事件不再与SDL对齐。
我的窗口大小变量是:
int canvasWidth = 800;
int canvasHeight = 600;
这是我的初始化代码:
void Init()
{
int i;
for (i = 0; i < 256; i++)
gpressed[i] = gWaspressed[i] = 0;
if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_noparaCHUTE) < 0)
{
fprintf(stderr,"Video initialization Failed: %s\n",SDL_GetError());
SDL_Quit();
exit(0);
}
SDL_GL_SetAttribute(SDL_GL_RED_SIZE,8);
SDL_GL_SetAttribute(SDL_GL_GREEN_SIZE,8);
SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE,8);
SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE,16);
SDL_GL_SetAttribute( SDL_GL_ALPHA_SIZE,5);
SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER,1);
int flags = SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN | SDL_WINDOW_RESIZABLE | SDL_WINDOW_ALLOW_HIGHDPI;
gSDLWindow = SDL_CreateWindow(
"",SDL_WINDOWPOS_CENTERED,800,600,flags);
SDL_SetRenderDrawColor(SDL_GetRenderer(gSDLWindow),0);
SDL_GLContext glcontext = SDL_GL_CreateContext(gSDLWindow);
SDL_GL_SetSwapInterval(1);
glViewport(0,canvasWidth,canvasHeight);
glewInit();
InitImGui();
framework_init_flat();
framework_init_tex();
atexit(SDL_Quit);
}
这是我的每帧更新代码:
void Update()
{
ImGuiIO& io = ImGui::GetIO();
// Setup resolution (every frame to accommodate for window resizing)
io.displaySize = ImVec2((float)canvasWidth,(float)canvasHeight);
SDL_SetwindowSize(gSDLWindow,canvasHeight);
// Setup time step
static double time = 0.0f;
const double current_time = SDL_GetTicks() / 1000.0;
if (current_time == time)
return;
io.DeltaTime = (float)(current_time - time);
time = current_time;
io.MousePos = ImVec2((float)gUIState.mousex,(float)gUIState.mousey);
io.MouseDown[0] = gUIState.mousedown != 0;
io.MouseDown[1] = 0;
if (gUIState.scroll)
{
io.MouseWheel += (float)gUIState.scroll * 0.5f;
gUIState.scroll = 0;
}
if (gUIState.textinput[0])
{
io.AddInputCharactersUTF8(gUIState.textinput);
gUIState.textinput[0] = 0;
}
for (int n = 0; n < 256; n++)
io.KeysDown[n] = gpressed[n] != 0;
io.KeyShift = ((SDL_GetModState() & KMOD_SHIFT) != 0);
io.KeyCtrl = ((SDL_GetModState() & KMOD_CTRL) != 0);
io.KeyAlt = ((SDL_GetModState() & KMOD_ALT) != 0);
}
解决方法
为什么不使用SDL窗口事件系统?这对我有用:
void update_screen_size(int w,int h)
{
glViewport(0,w,h);
}
void somewhere_in_your_main_loop()
{
SDL_Event event;
while (SDL_PollEvent(&event))
{
switch (event.type)
{
case SDL_QUIT:
emscripten_cancel_main_loop();
break;
case SDL_WINDOWEVENT:
if (event.window.event == SDL_WINDOWEVENT_RESIZED)
{
update_screen_size(event.window.data1,event.window.data2);
}
break;
default:
break;
}
}
}
另一种方法是在每一帧查询html canvas:
EM_JS(int,get_canvas_width,(),{ return canvas.width; });
EM_JS(int,get_canvas_height,{ return canvas.height; });
void somewhere_in_your_main_loop()
{
update_screen_size(get_canvass_width(),get_canvas_height());
}