static void DrawBackground(void) {
// Whole window cleared with clear color, checkerboard rendered on top of it.
glClear(GL_COLOR_BUFFER_BIT);
DrawCheckerBoard();
// ANIM background color rendered (blend) on top. Default is white for still
// images (without ANIM chunk). glClear() can't be used for that (no blend).
if (kParams.draw_anim_background_color) {
glPushMatrix();
glLoadIdentity();
glColor4f(GetColorf(kParams.bg_color, 16), // BGRA from spec
GetColorf(kParams.bg_color, 8),
GetColorf(kParams.bg_color, 0),
GetColorf(kParams.bg_color, 24));
glRecti(-1, -1, +1, +1);
glPopMatrix();
}
}
static void StartDisplay(void) {
const int width = kParams.canvas_width;
const int height = kParams.canvas_height;
glutInitDisplayMode(GLUT_RGBA);
glutInitWindowSize(width, height);
glutCreateWindow("WebP viewer");
glutDisplayFunc(HandleDisplay);
glutIdleFunc(NULL);
glutKeyboardFunc(HandleKey);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glEnable(GL_BLEND);
glClearColor(GetColorf(kParams.bg_color, 0),
GetColorf(kParams.bg_color, 8),
GetColorf(kParams.bg_color, 16),
GetColorf(kParams.bg_color, 24));
HandleReshape(width, height);
glClear(GL_COLOR_BUFFER_BIT);
DrawCheckerBoard();
}
