Windows: Pass the struct from BeginPaint() to EndPaint()

The documentation explains that the PAINTSTRUCT returned by BeginPaint() should
be passed to the corresponding call to EndPaint().  I'm not sure what
real-world effects not doing this had, but this commit fixes things to use the
API as intended.

4 files changed, 7 insertions, 12 deletions

diff --git a/src/win.c b/src/win.c
index 08eebec..75e0d71 100644
--- a/src/win.c
+++ b/src/win.c
@@ -1651,8 +1651,7 @@ PuglStatus
 puglWinEnter(PuglView* view, const PuglExposeEvent* expose)
 {
   if (expose) {
-    PAINTSTRUCT ps;
-    BeginPaint(view->impl->hwnd, &ps);
+    BeginPaint(view->impl->hwnd, &view->impl->paint);
   }
 
   return PUGL_SUCCESS;
@@ -1662,8 +1661,7 @@ PuglStatus
 puglWinLeave(PuglView* view, const PuglExposeEvent* expose)
 {
   if (expose) {
-    PAINTSTRUCT ps;
-    EndPaint(view->impl->hwnd, &ps);
+    EndPaint(view->impl->hwnd, &view->impl->paint);
   }
 
   return PUGL_SUCCESS;
diff --git a/src/win.h b/src/win.h
index 890d940..84f1d4e 100644
--- a/src/win.h
+++ b/src/win.h
@@ -25,6 +25,7 @@ struct PuglInternalsImpl {
   HCURSOR         cursor;
   HDC             hdc;
   WINDOWPLACEMENT oldPlacement;
+  PAINTSTRUCT     paint;
   PuglBlob        clipboard;
   PuglSurface*    surface;
   double          scaleFactor;
diff --git a/src/win_cairo.c b/src/win_cairo.c
index 4bef2e6..10e06e6 100644
--- a/src/win_cairo.c
+++ b/src/win_cairo.c
@@ -108,8 +108,7 @@ puglWinCairoEnter(PuglView* view, const PuglExposeEvent* expose)
 
   if (expose && !(st = puglWinCairoCreateDrawContext(view)) &&
       !(st = puglWinCairoOpen(view))) {
-    PAINTSTRUCT ps;
-    BeginPaint(view->impl->hwnd, &ps);
+    BeginPaint(view->impl->hwnd, &view->impl->paint);
   }
 
   return st;
@@ -136,8 +135,7 @@ puglWinCairoLeave(PuglView* view, const PuglExposeEvent* expose)
     puglWinCairoClose(view);
     puglWinCairoDestroyDrawContext(view);
 
-    PAINTSTRUCT ps;
-    EndPaint(view->impl->hwnd, &ps);
+    EndPaint(view->impl->hwnd, &view->impl->paint);
   }
 
   return PUGL_SUCCESS;
diff --git a/src/win_gl.c b/src/win_gl.c
index 0ca9909..293dd9b 100644
--- a/src/win_gl.c
+++ b/src/win_gl.c
@@ -264,8 +264,7 @@ puglWinGlEnter(PuglView* view, const PuglExposeEvent* expose)
   wglMakeCurrent(view->impl->hdc, surface->hglrc);
 
   if (expose) {
-    PAINTSTRUCT ps;
-    BeginPaint(view->impl->hwnd, &ps);
+    BeginPaint(view->impl->hwnd, &view->impl->paint);
   }
 
   return PUGL_SUCCESS;
@@ -275,8 +274,7 @@ static PuglStatus
 puglWinGlLeave(PuglView* view, const PuglExposeEvent* expose)
 {
   if (expose) {
-    PAINTSTRUCT ps;
-    EndPaint(view->impl->hwnd, &ps);
+    EndPaint(view->impl->hwnd, &view->impl->paint);
     SwapBuffers(view->impl->hdc);
   }