GTK: Don't create unnecessary drawing contexts

When surfaces are created without an explicit target surface they are
only used for measurement purposes, so don't create a unnecessary
drawing context out of the widget's surface.

This avoid calling gdk_cairo_create() outside a draw handler, which
GTK 3.14 stops allowing [1].

[1] https://mail.gnome.org/archives/gtk-devel-list/2014-June/msg00010.html

1 files changed, 9 insertions, 14 deletions

diff --git a/gtk/PlatGTK.cxx b/gtk/PlatGTK.cxx
index d4572a912..0b8eeaf92 100644
--- a/gtk/PlatGTK.cxx
+++ b/gtk/PlatGTK.cxx
@@ -549,20 +549,9 @@ bool SurfaceImpl::Initialised() {
 void SurfaceImpl::Init(WindowID wid) {
 	Release();
 	PLATFORM_ASSERT(wid);
-#if GTK_CHECK_VERSION(3,0,0)
-	GdkWindow *drawable_ = gtk_widget_get_window(PWidget(wid));
-#else
-	GdkDrawable *drawable_ = GDK_DRAWABLE(PWidget(wid)->window);
-#endif
-	if (drawable_) {
-		context = gdk_cairo_create(drawable_);
-		PLATFORM_ASSERT(context);
-	} else {
-		// Shouldn't happen with valid window but may when calls made before
-		// window completely allocated and mapped.
-		psurf = cairo_image_surface_create(CAIRO_FORMAT_RGB24, 1, 1);
-		context = cairo_create(psurf);
-	}
+	// if we are only created from a window ID, we can't perform drawing
+	psurf = 0;
+	context = 0;
 	createdGC = true;
 	pcontext = gtk_widget_create_pango_context(PWidget(wid));
 	PLATFORM_ASSERT(pcontext);
@@ -681,6 +670,7 @@ void SurfaceImpl::LineTo(int x_, int y_) {
 
 void SurfaceImpl::Polygon(Point *pts, int npts, ColourDesired fore,
                           ColourDesired back) {
+	PLATFORM_ASSERT(context);
 	PenColour(back);
 	cairo_move_to(context, pts[0].x + 0.5, pts[0].y + 0.5);
 	for (int i = 1; i < npts; i++) {
@@ -718,6 +708,7 @@ void SurfaceImpl::FillRectangle(PRectangle rc, Surface &surfacePattern) {
 	SurfaceImpl &surfi = static_cast<SurfaceImpl &>(surfacePattern);
 	bool canDraw = surfi.psurf;
 	if (canDraw) {
+		PLATFORM_ASSERT(context);
 		// Tile pattern over rectangle
 		// Currently assumes 8x8 pattern
 		int widthPat = 8;
@@ -803,6 +794,7 @@ void SurfaceImpl::AlphaRectangle(PRectangle rc, int cornerSize, ColourDesired fi
 }
 
 void SurfaceImpl::DrawRGBAImage(PRectangle rc, int width, int height, const unsigned char *pixelsImage) {
+	PLATFORM_ASSERT(context);
 	if (rc.Width() > width)
 		rc.left += (rc.Width() - width) / 2;
 	rc.right = rc.left + width;
@@ -837,6 +829,7 @@ void SurfaceImpl::DrawRGBAImage(PRectangle rc, int width, int height, const unsi
 }
 
 void SurfaceImpl::Ellipse(PRectangle rc, ColourDesired fore, ColourDesired back) {
+	PLATFORM_ASSERT(context);
 	PenColour(back);
 	cairo_arc(context, (rc.left + rc.right) / 2, (rc.top + rc.bottom) / 2,
 		Platform::Minimum(rc.Width(), rc.Height()) / 2, 0, 2*kPi);
@@ -849,6 +842,7 @@ void SurfaceImpl::Copy(PRectangle rc, Point from, Surface &surfaceSource) {
 	SurfaceImpl &surfi = static_cast<SurfaceImpl &>(surfaceSource);
 	bool canDraw = surfi.psurf;
 	if (canDraw) {
+		PLATFORM_ASSERT(context);
 		cairo_set_source_surface(context, surfi.psurf,
 			rc.left - from.x, rc.top - from.y);
 		cairo_rectangle(context, rc.left, rc.top, rc.right-rc.left, rc.bottom-rc.top);
@@ -1201,6 +1195,7 @@ XYPOSITION SurfaceImpl::AverageCharWidth(Font &font_) {
 }
 
 void SurfaceImpl::SetClip(PRectangle rc) {
+	PLATFORM_ASSERT(context);
 	cairo_rectangle(context, rc.left, rc.top, rc.right, rc.bottom);
 	cairo_clip(context);
 }