buffer: remove buffer->cairo

It's more common for cairo_t to have a temporary lifetime and it will
prevent accidentally reusing its previous state.

include/buffer.h

@@ -34,7 +34,6 @@ struct lab_data_buffer {
 
 	bool surface_owns_data;
 	cairo_surface_t *surface;
-	cairo_t *cairo;
 	void *data;
 	uint32_t format; /* currently always DRM_FORMAT_ARGB8888 */
 	size_t stride;

src/buffer.c

@@ -45,7 +45,6 @@ static void
 data_buffer_destroy(struct wlr_buffer *wlr_buffer)
 {
 	struct lab_data_buffer *buffer = data_buffer_from_buffer(wlr_buffer);
-	cairo_destroy(buffer->cairo);
 	/* this also frees buffer->data if surface_owns_data == true */
 	cairo_surface_destroy(buffer->surface);
 	if (!buffer->surface_owns_data) {
@@ -97,7 +96,6 @@ buffer_adopt_cairo_surface(cairo_surface_t *surface)
 	buffer->stride = cairo_image_surface_get_stride(buffer->surface);
 	buffer->logical_width = width;
 	buffer->logical_height = height;
-	buffer->cairo = cairo_create(surface);
 	buffer->surface_owns_data = true;
 
 	return buffer;
@@ -167,7 +165,7 @@ buffer_convert_cairo_surface_for_icon(cairo_surface_t *surface,
 		buffer = buffer_create_cairo(logical.width,
 			logical.height, scale);
 
-		cairo_t *cairo = buffer->cairo;
+		cairo_t *cairo = cairo_create(buffer->surface);
 		cairo_scale(cairo, (double)logical.width / width,
 			(double)logical.height / height);
 		cairo_set_source_surface(cairo, surface, 0, 0);
@@ -177,8 +175,9 @@ buffer_convert_cairo_surface_for_icon(cairo_surface_t *surface,
 
 		/* ensure pixel data is updated */
 		cairo_surface_flush(buffer->surface);
-		/* destroy original surface */
+		/* destroy original cairo surface & context */
 		cairo_surface_destroy(surface);
+		cairo_destroy(cairo);
 	}
 
 	return buffer;
@@ -197,7 +196,6 @@ buffer_create_from_data(void *pixel_data, uint32_t width, uint32_t height,
 	buffer->stride = stride;
 	buffer->surface = cairo_image_surface_create_for_data(
 		pixel_data, CAIRO_FORMAT_ARGB32, width, height, stride);
-	buffer->cairo = cairo_create(buffer->surface);
 	buffer->surface_owns_data = false;
 	return buffer;
 }

src/common/font.c

@@ -115,8 +115,8 @@ font_buffer_create(struct lab_data_buffer **buffer, int max_width,
 		return;
 	}
 
-	cairo_t *cairo = (*buffer)->cairo;
-	cairo_surface_t *surf = cairo_get_target(cairo);
+	cairo_surface_t *surf = (*buffer)->surface;
+	cairo_t *cairo = cairo_create(surf);
 
 	/*
 	 * Fill with the background color first IF the background color
@@ -171,6 +171,7 @@ font_buffer_create(struct lab_data_buffer **buffer, int max_width,
 	g_object_unref(layout);
 
 	cairo_surface_flush(surf);
+	cairo_destroy(cairo);
 }
 
 void

src/common/scaled-rect-buffer.c

@@ -39,7 +39,7 @@ _create_buffer(struct scaled_scene_buffer *scaled_buffer, double scale)
 		return NULL;
 	}
 
-	cairo_t *cairo = buffer->cairo;
+	cairo_t *cairo = cairo_create(buffer->surface);
 
 	/* Clear background */
 	cairo_set_operator(cairo, CAIRO_OPERATOR_CLEAR);
@@ -58,6 +58,8 @@ _create_buffer(struct scaled_scene_buffer *scaled_buffer, double scale)
 	set_cairo_color(cairo, self->border_color);
 	cairo_stroke(cairo);
 
+	cairo_destroy(cairo);
+
 	return buffer;
 }
 

src/img/img-svg.c

@@ -41,7 +41,7 @@ img_svg_load(const char *filename, struct lab_data_buffer **buffer, int size,
 
 	*buffer = buffer_create_cairo(size, size, scale);
 	cairo_surface_t *image = (*buffer)->surface;
-	cairo_t *cr = (*buffer)->cairo;
+	cairo_t *cr = cairo_create(image);
 
 	rsvg_handle_render_document(svg, cr, &viewport, &err);
 	if (err) {
@@ -55,6 +55,7 @@ img_svg_load(const char *filename, struct lab_data_buffer **buffer, int size,
 		goto error;
 	}
 	cairo_surface_flush(image);
+	cairo_destroy(cr);
 
 	g_object_unref(svg);
 	return;
@@ -62,5 +63,6 @@ img_svg_load(const char *filename, struct lab_data_buffer **buffer, int size,
 error:
 	wlr_buffer_drop(&(*buffer)->base);
 	*buffer = NULL;
+	cairo_destroy(cr);
 	g_object_unref(svg);
 }

src/osd.c

@@ -354,8 +354,9 @@ display_osd(struct output *output, struct wl_array *views)
 	}
 
 	/* Render OSD image */
-	cairo_t *cairo = buffer->cairo;
+	cairo_t *cairo = cairo_create(buffer->surface);
 	render_osd(server, cairo, w, h, show_workspace, workspace_name, views);
+	cairo_destroy(cairo);
 
 	struct wlr_scene_buffer *scene_buffer = wlr_scene_buffer_create(
 		output->osd_tree, &buffer->base);

src/theme.c

@@ -80,7 +80,12 @@ zdrop(struct lab_data_buffer **buffer)
 	}
 }
 
-static struct lab_data_buffer *
+struct icon_drawing_context {
+	struct lab_data_buffer *buffer;
+	cairo_t *cairo;
+};
+
+static struct icon_drawing_context
 copy_icon_buffer(struct theme *theme, struct lab_data_buffer *icon_buffer)
 {
 	assert(icon_buffer);
@@ -110,7 +115,7 @@ copy_icon_buffer(struct theme *theme, struct lab_data_buffer *icon_buffer)
 	int buffer_height = (double)height * scale;
 	struct lab_data_buffer *buffer = buffer_create_cairo(
 		buffer_width, buffer_height, 1.0);
-	cairo_t *cairo = buffer->cairo;
+	cairo_t *cairo = cairo_create(buffer->surface);
 
 	cairo_set_source_surface(cairo, surface,
 		(buffer_width - icon_width) / 2, (buffer_height - icon_height) / 2);
@@ -122,7 +127,10 @@ copy_icon_buffer(struct theme *theme, struct lab_data_buffer *icon_buffer)
 	 */
 	cairo_scale(cairo, scale, scale);
 
-	return buffer;
+	return (struct icon_drawing_context){
+		.buffer = buffer,
+		.cairo = cairo,
+	};
 }
 
 static void
@@ -136,8 +144,9 @@ create_hover_fallback(struct theme *theme,
 	int width = theme->window_button_width;
 	int height = theme->window_button_height;
 
-	*hover_buffer = copy_icon_buffer(theme, icon_buffer);
-	cairo_t *cairo = (*hover_buffer)->cairo;
+	struct icon_drawing_context ctx = copy_icon_buffer(theme, icon_buffer);
+	*hover_buffer = ctx.buffer;
+	cairo_t *cairo = ctx.cairo;
 
 	/* Overlay (pre-multiplied alpha) */
 	float overlay_color[4] = { 0.15f, 0.15f, 0.15f, 0.3f};
@@ -156,6 +165,7 @@ create_hover_fallback(struct theme *theme,
 	cairo_fill(cairo);
 
 	cairo_surface_flush(cairo_get_target(cairo));
+	cairo_destroy(cairo);
 }
 
 static void
@@ -163,8 +173,9 @@ create_rounded_buffer(struct theme *theme, enum corner corner,
 		struct lab_data_buffer **rounded_buffer,
 		struct lab_data_buffer *icon_buffer)
 {
-	*rounded_buffer = copy_icon_buffer(theme, icon_buffer);
-	cairo_t *cairo = (*rounded_buffer)->cairo;
+	struct icon_drawing_context ctx = copy_icon_buffer(theme, icon_buffer);
+	*rounded_buffer = ctx.buffer;
+	cairo_t *cairo = ctx.cairo;
 
 	int width = theme->window_button_width;
 	int height = theme->window_button_height;
@@ -189,12 +200,13 @@ create_rounded_buffer(struct theme *theme, enum corner corner,
 	};
 	struct lab_data_buffer *mask_buffer = rounded_rect(&rounded_ctx);
 	cairo_set_operator(cairo, CAIRO_OPERATOR_DEST_IN);
-	cairo_set_source_surface(cairo, cairo_get_target(mask_buffer->cairo),
+	cairo_set_source_surface(cairo, mask_buffer->surface,
 		(corner == LAB_CORNER_TOP_LEFT) ? -margin_x : 0,
 		-margin_y);
 	cairo_paint(cairo);
 
 	cairo_surface_flush(cairo_get_target(cairo));
+	cairo_destroy(cairo);
 	wlr_buffer_drop(&mask_buffer->base);
 }
 
@@ -1088,8 +1100,8 @@ rounded_rect(struct rounded_corner_ctx *ctx)
 	/* TODO: scale */
 	buffer = buffer_create_cairo(w, h, 1);
 
-	cairo_t *cairo = buffer->cairo;
-	cairo_surface_t *surf = cairo_get_target(cairo);
+	cairo_surface_t *surf = buffer->surface;
+	cairo_t *cairo = cairo_create(surf);
 
 	/* set transparent background */
 	cairo_set_operator(cairo, CAIRO_OPERATOR_CLEAR);
@@ -1231,6 +1243,7 @@ rounded_rect(struct rounded_corner_ctx *ctx)
 
 out:
 	cairo_surface_flush(surf);
+	cairo_destroy(cairo);
 
 	return buffer;
 }

src/workspaces.c

@@ -90,7 +90,7 @@ _osd_update(struct server *server)
 			continue;
 		}
 
-		cairo = buffer->cairo;
+		cairo = cairo_create(buffer->surface);
 
 		/* Background */
 		set_cairo_color(cairo, theme->osd_bg_color);
@@ -150,6 +150,7 @@ _osd_update(struct server *server)
 		g_object_unref(layout);
 		surface = cairo_get_target(cairo);
 		cairo_surface_flush(surface);
+		cairo_destroy(cairo);
 
 		if (!output->workspace_osd) {
 			output->workspace_osd = wlr_scene_buffer_create(