Commit 54685787ca7677d711cabe355a29d78627362223
2017-09-26T15:07:35
Fixed bug 3847 - Hit Test x coordinate wrong on secondary monitor Robert Turner SDL_windowsevents.c contains code to retrieve the x and y coordinate for a requested hit test. It does this as follows: POINT winpoint = { (int) LOWORD(lParam), (int) HIWORD(lParam) }; LOWORD(lParam) does not correctly mask off high bits that are set if the point is on a second (or third, etc.) monitor. This effectively offsets the x-coordinate by a large value. MSDN documentation suggests that LOWORD() and HIWORD() are the wrong macros for the task, instead suggesting we should be doing something like the following: POINT winpoint = { GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam) }; Testing this change on my Windows 10 machine with 2 monitors gives the correct results.
diff --git a/src/video/windows/SDL_windowsevents.c b/src/video/windows/SDL_windowsevents.c
index 015ae88..b73e9df 100644
--- a/src/video/windows/SDL_windowsevents.c
+++ b/src/video/windows/SDL_windowsevents.c
@@ -961,7 +961,7 @@ WIN_WindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
SDL_Window *window = data->window;
if (window->hit_test) {
- POINT winpoint = { (int) LOWORD(lParam), (int) HIWORD(lParam) };
+ POINT winpoint = { GET_X_LPARAM(lParam), GET_Y_LPARAM(lParam) };
if (ScreenToClient(hwnd, &winpoint)) {
const SDL_Point point = { (int) winpoint.x, (int) winpoint.y };
const SDL_HitTestResult rc = window->hit_test(window, &point, window->hit_test_data);