Fix partial exposure in X11 Cairo backend

1 files changed, 35 insertions, 10 deletions

diff --git a/src/x11_cairo.c b/src/x11_cairo.c
index be9ae09..eabf46f 100644
--- a/src/x11_cairo.c
+++ b/src/x11_cairo.c
@@ -1,6 +1,7 @@
-// Copyright 2012-2022 David Robillard <d@drobilla.net>
+// Copyright 2012-2023 David Robillard <d@drobilla.net>
 // SPDX-License-Identifier: ISC
 
+#include "macros.h"
 #include "types.h"
 #include "x11.h"
 
@@ -11,7 +12,6 @@
 #include <cairo-xlib.h>
 #include <cairo.h>
 
-#include <math.h>
 #include <stdlib.h>
 
 typedef struct {
@@ -20,6 +20,24 @@ typedef struct {
   cairo_t*         cr;
 } PuglX11CairoSurface;
 
+static PuglViewSize
+puglX11CairoGetViewSize(const PuglView* const view)
+{
+  PuglViewSize size = {0U, 0U};
+
+  if (view->lastConfigure.type == PUGL_CONFIGURE) {
+    // Use the size of the last configured frame
+    size.width  = view->lastConfigure.width;
+    size.height = view->lastConfigure.height;
+  } else {
+    // Use the default size
+    size.width  = view->sizeHints[PUGL_DEFAULT_SIZE].width;
+    size.height = view->sizeHints[PUGL_DEFAULT_SIZE].height;
+  }
+
+  return size;
+}
+
 static void
 puglX11CairoClose(PuglView* view)
 {
@@ -32,14 +50,10 @@ puglX11CairoClose(PuglView* view)
 }
 
 static PuglStatus
-puglX11CairoOpen(PuglView*    view,
-                 const double expose_width,
-                 const double expose_height)
+puglX11CairoOpen(PuglView* view, const PuglSpan width, const PuglSpan height)
 {
   PuglInternals* const       impl    = view->impl;
   PuglX11CairoSurface* const surface = (PuglX11CairoSurface*)impl->surface;
-  const int                  width   = (int)ceil(expose_width);
-  const int                  height  = (int)ceil(expose_height);
 
   surface->back = cairo_xlib_surface_create(
     view->world->impl->display, impl->win, impl->vi->visual, width, height);
@@ -83,9 +97,20 @@ puglX11CairoEnter(PuglView* view, const PuglExposeEvent* expose)
   PuglX11CairoSurface* const surface = (PuglX11CairoSurface*)impl->surface;
   PuglStatus                 st      = PUGL_SUCCESS;
 
-  if (expose && !(st = puglX11CairoOpen(view, expose->width, expose->height))) {
-    surface->cr = cairo_create(surface->front);
-    st = cairo_status(surface->cr) ? PUGL_CREATE_CONTEXT_FAILED : PUGL_SUCCESS;
+  if (expose) {
+    const PuglViewSize viewSize      = puglX11CairoGetViewSize(view);
+    const PuglSpan     right         = expose->x + expose->width;
+    const PuglSpan     bottom        = expose->y + expose->height;
+    const PuglSpan     surfaceWidth  = MAX(right, viewSize.width);
+    const PuglSpan     surfaceHeight = MAX(bottom, viewSize.height);
+    if (!(st = puglX11CairoOpen(view, surfaceWidth, surfaceHeight))) {
+      surface->cr = cairo_create(surface->front);
+      if (cairo_status(surface->cr)) {
+        cairo_destroy(surface->cr);
+        surface->cr = NULL;
+        st          = PUGL_CREATE_CONTEXT_FAILED;
+      }
+    }
   }
 
   return st;