pugl.patch

diff --git a/src/win_cairo.c b/src/win_cairo.c
index 0aab254..ee7fd31 100644
--- a/src/win_cairo.c
+++ b/src/win_cairo.c
@@ -13,42 +13,12 @@
 #include <stdlib.h>
 
 typedef struct {
-  cairo_surface_t* surface;
   cairo_t*         cr;
-  HDC              drawDc;
-  HBITMAP          drawBitmap;
+  cairo_surface_t* image_surface;
+  int              width;
+  int              height;
 } PuglWinCairoSurface;
 
-static PuglStatus
-puglWinCairoCreateDrawContext(PuglView* view)
-{
-  PuglInternals* const       impl    = view->impl;
-  PuglWinCairoSurface* const surface = (PuglWinCairoSurface*)impl->surface;
-
-  surface->drawDc     = CreateCompatibleDC(impl->hdc);
-  surface->drawBitmap = CreateCompatibleBitmap(
-    impl->hdc, (int)view->lastConfigure.width, (int)view->lastConfigure.height);
-
-  DeleteObject(SelectObject(surface->drawDc, surface->drawBitmap));
-
-  return PUGL_SUCCESS;
-}
-
-static PuglStatus
-puglWinCairoDestroyDrawContext(PuglView* view)
-{
-  PuglInternals* const       impl    = view->impl;
-  PuglWinCairoSurface* const surface = (PuglWinCairoSurface*)impl->surface;
-
-  DeleteDC(surface->drawDc);
-  DeleteObject(surface->drawBitmap);
-
-  surface->drawDc     = NULL;
-  surface->drawBitmap = NULL;
-
-  return PUGL_SUCCESS;
-}
-
 static PuglStatus
 puglWinCairoConfigure(PuglView* view)
 {
@@ -67,10 +37,10 @@ puglWinCairoClose(PuglView* view)
 {
   PuglInternals* const       impl    = view->impl;
   PuglWinCairoSurface* const surface = (PuglWinCairoSurface*)impl->surface;
-
-  cairo_surface_destroy(surface->surface);
-
-  surface->surface = NULL;
+  cairo_destroy (surface->cr);
+  cairo_surface_destroy(surface->image_surface);
+  surface->cr = NULL;
+  surface->image_surface = NULL;
 }
 
 static PuglStatus
@@ -79,9 +49,10 @@ puglWinCairoOpen(PuglView* view)
   PuglInternals* const       impl    = view->impl;
   PuglWinCairoSurface* const surface = (PuglWinCairoSurface*)impl->surface;
 
-  if (!(surface->surface = cairo_win32_surface_create(surface->drawDc)) ||
-      cairo_surface_status(surface->surface) ||
-      !(surface->cr = cairo_create(surface->surface)) ||
+  if (!(surface->image_surface = cairo_image_surface_create(CAIRO_FORMAT_ARGB32,
+                    (int)view->lastConfigure.width, (int)view->lastConfigure.height)) ||
+      cairo_surface_status(surface->image_surface) ||
+      !(surface->cr = cairo_create(surface->image_surface)) ||
       cairo_status(surface->cr)) {
     return PUGL_CREATE_CONTEXT_FAILED;
   }
@@ -89,6 +60,44 @@ puglWinCairoOpen(PuglView* view)
   return PUGL_SUCCESS;
 }
 
+static PuglStatus
+puglWinCairoCheckResize(PuglView* view)
+{
+  PuglStatus st = PUGL_SUCCESS;
+  PuglInternals* const       impl    = view->impl;
+  PuglWinCairoSurface* const surface = (PuglWinCairoSurface*)impl->surface;
+
+  // check if the size have changed, if so recreate the image surface
+  // to match the new size
+  if (surface->width != (int)view->lastConfigure.width ||
+    surface->height != (int)view->lastConfigure.height) {
+      surface->width = (int)view->lastConfigure.width;
+      surface->height = (int)view->lastConfigure.height;
+      puglWinCairoClose(view);
+      st = puglWinCairoOpen(view);
+  } else {
+      // when reuse the image surface clean up the old content
+      cairo_set_operator(surface->cr, CAIRO_OPERATOR_CLEAR);
+      cairo_paint(surface->cr);
+      cairo_set_operator(surface->cr, CAIRO_OPERATOR_OVER);
+  }
+
+  return st;
+}
+
+static PuglStatus
+puglWinCairoCreate(PuglView* view)
+{
+  PuglInternals* const       impl    = view->impl;
+  PuglWinCairoSurface* const surface = (PuglWinCairoSurface*)impl->surface;
+
+  // get the default size and create the image surface
+  surface->width = (int)view->lastConfigure.width;
+  surface->height = (int)view->lastConfigure.height;
+
+  return puglWinCairoOpen(view);
+}
+
 static void
 puglWinCairoDestroy(PuglView* view)
 {
@@ -96,7 +105,6 @@ puglWinCairoDestroy(PuglView* view)
   PuglWinCairoSurface* const surface = (PuglWinCairoSurface*)impl->surface;
 
   puglWinCairoClose(view);
-  puglWinCairoDestroyDrawContext(view);
   free(surface);
   impl->surface = NULL;
 }
@@ -106,9 +114,8 @@ puglWinCairoEnter(PuglView* view, const PuglExposeEvent* expose)
 {
   PuglStatus st = PUGL_SUCCESS;
 
-  if (expose && !(st = puglWinCairoCreateDrawContext(view)) &&
-      !(st = puglWinCairoOpen(view))) {
-    st = puglWinEnter(view, expose);
+  if (expose) {
+      st = puglWinCairoCheckResize(view);
   }
 
   return st;
@@ -121,19 +128,13 @@ puglWinCairoLeave(PuglView* view, const PuglExposeEvent* expose)
   PuglWinCairoSurface* const surface = (PuglWinCairoSurface*)impl->surface;
 
   if (expose) {
-    cairo_surface_flush(surface->surface);
-    BitBlt(impl->hdc,
-           0,
-           0,
-           (int)view->lastConfigure.width,
-           (int)view->lastConfigure.height,
-           surface->drawDc,
-           0,
-           0,
-           SRCCOPY);
-
-    puglWinCairoClose(view);
-    puglWinCairoDestroyDrawContext(view);
+      HDC hdc = BeginPaint(impl->hwnd, &impl->paint);
+      cairo_surface_t* win_surface = cairo_win32_surface_create(hdc);
+      cairo_t* cri = cairo_create(win_surface);
+      cairo_set_source_surface(cri, surface->image_surface, 0.0, 0.0);
+      cairo_paint(cri);
+      cairo_destroy(cri);
+      cairo_surface_destroy(win_surface);
   }
 
   return puglWinLeave(view, expose);
@@ -149,7 +150,7 @@ const PuglBackend*
 puglCairoBackend(void)
 {
   static const PuglBackend backend = {puglWinCairoConfigure,
-                                      puglStubCreate,
+                                      puglWinCairoCreate,
                                       puglWinCairoDestroy,
                                       puglWinCairoEnter,
                                       puglWinCairoLeave,