kc3-lang/SDL

2022-01-21T17:15:18

Fix the erroneous generation of mouse-down events from touch-move events. The issue is that MS Windows synthesizes a mouse-move event in response to touch-move events, and those mouse-move events are NOT labeled as coming from a touch (e.g. GetMouseMessageSource() will not return SDL_MOUSE_EVENT_SOURCE_TOUCH for those synthesized mouse-move events). In addition, there seems to be no way to prevent this from happening; https://gist.github.com/vbfox/1339671 claims to demonstrate a technique to prevent it, but in my experience, it doesn't work. Because of this, the "fallthrough" case can't test that the synthesized mouse-move came from a touch-move, and starts erroneously pressing down the mouse-button, leading to massive confusion in the client application.

diff --git a/src/video/windows/SDL_windowsevents.c b/src/video/windows/SDL_windowsevents.c
index 471bbee..34cbcac 100644
--- a/src/video/windows/SDL_windowsevents.c
+++ b/src/video/windows/SDL_windowsevents.c
@@ -732,8 +732,8 @@ WIN_WindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
                 }
             }
         }
-        /* don't break here, fall through to check the wParam like the button presses */
-        SDL_FALLTHROUGH;
+        break;
+
     case WM_LBUTTONUP:
     case WM_RBUTTONUP:
     case WM_MBUTTONUP: