fix hidpi support, add comments

1 files changed, 34 insertions, 3 deletions

diff --git a/main.c b/main.c
index 76811ec..fa61427 100644
--- a/main.c
+++ b/main.c
@@ -116,8 +116,22 @@ link_compute_program(
 }
 #endif
 
+static void
+update_viewport(
+  SDL_Window *win
+) {
+  int w, h;
+
+  // get window drawable size
+  SDL_GL_GetDrawableSize(win, &w, &h);
+
+  // set viewport size
+  glViewport(0, 0, w, h);
+}
+
 static SDL_Window *
 init(void) {
+  // init sdl
   if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER) < 0) {
     SDL_Log("SDL_Init() failed: %s", SDL_GetError());
     exit(EXIT_FAILURE);
@@ -168,7 +182,7 @@ init(void) {
   }
 
   // init glew
-  // (do this immediately after setting context)
+  // (do this immediately after GL context init)
   {
     GLenum err = glewInit();
     if (err != GLEW_OK) {
@@ -177,6 +191,10 @@ init(void) {
     }
   }
 
+  // set viewport size
+  // (after GLEW init)
+  update_viewport(win);
+
   // set swap interval
   // (after context init)
   if (SDL_GL_SetSwapInterval(1) < 0) {
@@ -195,12 +213,14 @@ static Uint32 timer_cb(
   SDL_Event ev;
   UNUSED(arg);
 
+  // build synthetic event
   ev.type = SDL_USEREVENT;
   ev.user.type = SDL_USEREVENT;
   ev.user.code = EVENT_CODE_TIMER;
   ev.user.data1 = NULL;
   ev.user.data2 = NULL;
 
+  // add event to queue
   SDL_PushEvent(&ev);
 
   // return interval
@@ -287,6 +307,7 @@ int main(int argc, char *argv[]) {
           break;
         case SDL_KEYDOWN:
           switch (ev.key.keysym.sym) {
+          case SDLK_q:
           case SDLK_ESCAPE:
             done = true;
 
@@ -310,8 +331,18 @@ int main(int argc, char *argv[]) {
         case SDL_WINDOWEVENT:
           switch (ev.window.event) {
           case SDL_WINDOWEVENT_SIZE_CHANGED:
-            // update viewport
-            glViewport(0, 0, ev.window.data1, ev.window.data2);
+            {
+              // map event to window
+              SDL_Window *win = SDL_GetWindowFromID(ev.window.windowID);
+
+              if (win) {
+                // update viewport
+                update_viewport(win);
+              } else {
+                SDL_Log("ignoring SIZE_CHANGED event from unknown window");
+              }
+            }
+
             break;
           }