Improve error handling when creating cairo image surfaces

Stop showing the perpetual and harmless cairo introspection error

Should give us more info for errors like #241, and default to drawing a
black background on the content drawing area

pympress/scribble.py

@@ -404,14 +404,26 @@ def reset_scribble_cache(self):
         window = self.c_da.get_window()
 
         if window is None:
-            return ValueError('Cannot initialize scribble acche without drawing area window')
+            return ValueError('Cannot initialize scribble cache without drawing area window')
 
         scale = window.get_scale_factor()
         ww, wh = self.c_da.get_allocated_width() * scale, self.c_da.get_allocated_height() * scale
         try:
             self.scribble_cache = window.create_similar_image_surface(cairo.Format.ARGB32, ww, wh, scale)
-        except ValueError:
-            logger.exception('Error creating highlight cache')
+        except ValueError as e:
+            if e.args == ('invalid enum value: 5',):
+                # Just try again as this error seems to always happen at the first call but not later on
+                # This is the gi introspection of cairo not accepting the value Format.RGB30 (???)
+                try:
+                    self.scribble_cache = window.create_similar_image_surface(cairo.Format.ARGB32, ww, wh, scale)
+                except ValueError:
+                    return
+            else:
+                logger.exception('Error creating highlight cache')
+        except cairo.Error:
+            logger.warning('Failed creating an ARGB32 surface sized {}x{} scale {} for highlight cache'
+                           .format(ww, wh, scale), exc_info=True)
+            return
         self.next_render = 0
 
 

pympress/surfacecache.py

@@ -254,7 +254,13 @@ def _create_surface(self, widget, fmt, width, height):
         """
         window = widget.get_window()
         scale = window.get_scale_factor()
-        return window.create_similar_image_surface(fmt, width * scale, height * scale, scale)
+        try:
+            return window.create_similar_image_surface(fmt, width * scale, height * scale, scale)
+        except cairo.Error:
+            logger.warning('Failed creating a {} cache surface sized {}x{} scale {} for widget {}'
+                           .format(fmt, width * scale, height * scale, scale, widget.get_name()), exc_info=True)
+            # Warn here but handle error at the call site
+            raise
 
 
     def prerender(self, page_nb):
@@ -306,6 +312,8 @@ def renderer(self, widget_name, page_nb):
         except AttributeError:
             logger.warning('Widget {} was not mapped when rendering'.format(widget_name), exc_info = True)
             return GLib.SOURCE_REMOVE
+        except cairo.Error:
+            return GLib.SOURCE_REMOVE
 
         context = cairo.Context(surface)
         page.render_cairo(context, ww, wh, wtype)

pympress/ui.py

@@ -1288,7 +1288,18 @@ def on_draw(self, widget, cairo_context):
                 return
 
             # Cache miss: render the page, and save it to the cache
-            pb = window.create_similar_image_surface(cairo.Format.RGB24, ww * scale, wh * scale, scale)
+            try:
+                pb = window.create_similar_image_surface(cairo.Format.RGB24, ww * scale, wh * scale, scale)
+            except cairo.Error:
+                logger.warning('Failed creating an RGB24 surface sized {}x{} scale {} for widget {}'
+                               .format(ww * scale, wh * scale, scale, name), exc_info=True)
+                if widget is self.c_da:
+                    cairo_context.save()
+                    cairo_context.set_source_rgb(0, 0, 0)
+                    cairo_context.fill()
+                    cairo_context.paint()
+                    cairo_context.restore()
+                return
 
             cairo_prerender = cairo.Context(pb)
             cairo_prerender.transform(zoom_matrix)