Extract a function

fiv-io.c

@@ -393,6 +393,87 @@ struct load_wuffs_frame_context {
 	FivIoImage *restore_previous;       ///< Canvas before the previous frame
 };
 
+static bool
+load_wuffs_frame_compose(struct load_wuffs_frame_context *ctx,
+	FivIoImage **image, const wuffs_base__frame_config *fc, GError **error)
+{
+	// Copy the previous frame to a new image.
+	FivIoImage *prev = ctx->result_tail, *canvas = fiv_io_image_new(
+		prev->format, prev->width, prev->height);
+	if (!canvas) {
+		set_error(error, "image allocation failure");
+		return false;
+	}
+
+	FivIoImage *base = ctx->restore_previous ? ctx->restore_previous : prev;
+	memcpy(canvas->data, base->data, base->stride * base->height);
+	g_clear_pointer(&ctx->restore_previous, fiv_io_image_unref);
+
+	// Apply that frame's disposal method.
+	// XXX: We do not expect opaque pictures to receive holes this way.
+	wuffs_base__rect_ie_u32 bounds =
+		wuffs_base__frame_config__bounds(&ctx->last_fc);
+	// TODO(p): This field needs to be colour-managed.
+	wuffs_base__color_u32_argb_premul bg =
+		wuffs_base__frame_config__background_color(&ctx->last_fc);
+
+	double a = (bg >> 24) / 255., r = 0, g = 0, b = 0;
+	if (a) {
+		r = (uint8_t) (bg >> 16) / 255. / a;
+		g = (uint8_t) (bg >> 8)  / 255. / a;
+		b = (uint8_t) (bg)       / 255. / a;
+	}
+
+	cairo_surface_t *surface = fiv_io_image_to_surface_noref(canvas);
+	cairo_t *cr = cairo_create(surface);
+	cairo_surface_destroy(surface);
+	if (wuffs_base__frame_config__disposal(&ctx->last_fc) ==
+			WUFFS_BASE__ANIMATION_DISPOSAL__RESTORE_BACKGROUND) {
+		cairo_rectangle(cr, bounds.min_incl_x, bounds.min_incl_y,
+			bounds.max_excl_x - bounds.min_incl_x,
+			bounds.max_excl_y - bounds.min_incl_y);
+		cairo_set_source_rgba(cr, r, g, b, a);
+		cairo_set_operator(cr, CAIRO_OPERATOR_SOURCE);
+		cairo_fill(cr);
+	}
+
+	if (wuffs_base__frame_config__disposal(fc) ==
+		WUFFS_BASE__ANIMATION_DISPOSAL__RESTORE_PREVIOUS) {
+		ctx->restore_previous = fiv_io_image_new(
+			canvas->format, canvas->width, canvas->height);
+		if (!ctx->restore_previous) {
+			cairo_destroy(cr);
+			fiv_io_image_unref(canvas);
+			set_error(error, "image allocation failure");
+			return false;
+		}
+		memcpy(ctx->restore_previous->data, canvas->data,
+			canvas->stride * canvas->height);
+	}
+
+	// Paint the current frame over that, within its bounds.
+	bounds = wuffs_base__frame_config__bounds(fc);
+	cairo_rectangle(cr, bounds.min_incl_x, bounds.min_incl_y,
+		bounds.max_excl_x - bounds.min_incl_x,
+		bounds.max_excl_y - bounds.min_incl_y);
+	cairo_clip(cr);
+
+	cairo_set_operator(cr,
+		wuffs_base__frame_config__overwrite_instead_of_blend(fc)
+			? CAIRO_OPERATOR_SOURCE
+			: CAIRO_OPERATOR_OVER);
+
+	surface = fiv_io_image_to_surface_noref(*image);
+	cairo_set_source_surface(cr, surface, 0, 0);
+	cairo_surface_destroy(surface);
+	cairo_paint(cr);
+	cairo_destroy(cr);
+
+	fiv_io_image_unref(*image);
+	*image = canvas;
+	return true;
+}
+
 static bool
 load_wuffs_frame(struct load_wuffs_frame_context *ctx, GError **error)
 {
@@ -491,84 +572,9 @@ load_wuffs_frame(struct load_wuffs_frame_context *ctx, GError **error)
 	}
 
 	// Single-frame images get a fast path, animations are are handled slowly:
-	if (wuffs_base__frame_config__index(&fc) > 0) {
-		// Copy the previous frame to a new image.
-		FivIoImage *prev = ctx->result_tail, *canvas = fiv_io_image_new(
-			prev->format, prev->width, prev->height);
-		if (!canvas) {
-			set_error(error, "image allocation failure");
-			goto fail;
-		}
-
-		FivIoImage *base = ctx->restore_previous
-			? ctx->restore_previous
-			: prev;
-		memcpy(canvas->data, base->data, base->stride * base->height);
-		g_clear_pointer(&ctx->restore_previous, fiv_io_image_unref);
-
-		// Apply that frame's disposal method.
-		// XXX: We do not expect opaque pictures to receive holes this way.
-		wuffs_base__rect_ie_u32 bounds =
-			wuffs_base__frame_config__bounds(&ctx->last_fc);
-		// TODO(p): This field needs to be colour-managed.
-		wuffs_base__color_u32_argb_premul bg =
-			wuffs_base__frame_config__background_color(&ctx->last_fc);
-
-		double a = (bg >> 24) / 255., r = 0, g = 0, b = 0;
-		if (a) {
-			r = (uint8_t) (bg >> 16) / 255. / a;
-			g = (uint8_t) (bg >> 8)  / 255. / a;
-			b = (uint8_t) (bg)       / 255. / a;
-		}
-
-		cairo_surface_t *surface = fiv_io_image_to_surface_noref(canvas);
-		cairo_t *cr = cairo_create(surface);
-		cairo_surface_destroy(surface);
-		if (wuffs_base__frame_config__disposal(&ctx->last_fc) ==
-				WUFFS_BASE__ANIMATION_DISPOSAL__RESTORE_BACKGROUND) {
-			cairo_rectangle(cr, bounds.min_incl_x, bounds.min_incl_y,
-				bounds.max_excl_x - bounds.min_incl_x,
-				bounds.max_excl_y - bounds.min_incl_y);
-			cairo_set_source_rgba(cr, r, g, b, a);
-			cairo_set_operator(cr, CAIRO_OPERATOR_SOURCE);
-			cairo_fill(cr);
-		}
-
-		if (wuffs_base__frame_config__disposal(&fc) ==
-			WUFFS_BASE__ANIMATION_DISPOSAL__RESTORE_PREVIOUS) {
-			ctx->restore_previous = fiv_io_image_new(
-				canvas->format, canvas->width, canvas->height);
-			if (!ctx->restore_previous) {
-				cairo_destroy(cr);
-				fiv_io_image_unref(canvas);
-				set_error(error, "image allocation failure");
-				goto fail;
-			}
-			memcpy(ctx->restore_previous->data, canvas->data,
-				canvas->stride * canvas->height);
-		}
-
-		// Paint the current frame over that, within its bounds.
-		bounds = wuffs_base__frame_config__bounds(&fc);
-		cairo_rectangle(cr, bounds.min_incl_x, bounds.min_incl_y,
-			bounds.max_excl_x - bounds.min_incl_x,
-			bounds.max_excl_y - bounds.min_incl_y);
-		cairo_clip(cr);
-
-		cairo_set_operator(cr,
-			wuffs_base__frame_config__overwrite_instead_of_blend(&fc)
-				? CAIRO_OPERATOR_SOURCE
-				: CAIRO_OPERATOR_OVER);
-
-		surface = fiv_io_image_to_surface_noref(image);
-		cairo_set_source_surface(cr, surface, 0, 0);
-		cairo_surface_destroy(surface);
-		cairo_paint(cr);
-		cairo_destroy(cr);
-
-		fiv_io_image_unref(image);
-		image = canvas;
-	}
+	if (wuffs_base__frame_config__index(&fc) > 0 &&
+		!load_wuffs_frame_compose(ctx, &image, &fc, error))
+		goto fail;
 
 	if (ctx->meta_exif)
 		image->exif = g_bytes_ref(ctx->meta_exif);