Backends: SDL: Report a zero display-size when window is minimized, consistent with other backends.

docs/CHANGELOG.txt

@@ -58,6 +58,8 @@ Other Changes:
   drag source uses _SourceNoPreviewTooltip flags. (#3160) [@rokups]
 - Backends: Win32: Support for #define NOGDI, won't try to call GetDeviceCaps(). (#3137, #2327)
 - Backends: Win32: Fix _WIN32_WINNT < 0x0600 (MinGW defaults to 0x502 == Windows 2003). (#3183)
+- Backends: SDL: Report a zero display-size when window is minimized, consistent with other backends,
+  making more render/clipping code use an early out path.
 - Backends: OpenGL: Fixed handling of GL 4.5+ glClipControl(GL_UPPER_LEFT) by inverting the
   projection matrix top and bottom values. (#3143, #3146) [@u3shit]
 - Backends: OpenGL: On OSX, if unspecified by app, made default GLSL version 150. (#3199) [@albertvaka]

examples/imgui_impl_sdl.cpp

@@ -17,6 +17,7 @@
 
 // CHANGELOG
 // (minor and older changes stripped away, please see git history for details)
+//  2020-05-25: Misc: Report a zero display-size when window is minimized, to be consistent with other backends.
 //  2020-02-20: Inputs: Fixed mapping for ImGuiKey_KeyPadEnter (using SDL_SCANCODE_KP_ENTER instead of SDL_SCANCODE_RETURN2).
 //  2019-12-17: Inputs: On Wayland, use SDL_GetMouseState (because there is no global mouse state).
 //  2019-12-05: Inputs: Added support for ImGuiMouseCursor_NotAllowed mouse cursor.
@@ -348,6 +349,8 @@ void ImGui_ImplSDL2_NewFrame(SDL_Window* window)
     int w, h;
     int display_w, display_h;
     SDL_GetWindowSize(window, &w, &h);
+    if (SDL_GetWindowFlags(window) & SDL_WINDOW_MINIMIZED)
+        w = h = 0;
     SDL_GL_GetDrawableSize(window, &display_w, &display_h);
     io.DisplaySize = ImVec2((float)w, (float)h);
     if (w > 0 && h > 0)