Patch for cairo-win32-font.c, when GetTextMetrics fails

Hello,

attached is a patch for cairo-win32-font.c, which fixed an issue with a problematic font on windows I had during printing a pdf document on cairo (not using poppler).

Problem:
Cairo uses the winapi GetTextMetrics function, but didn’t check, if the function succeeded. See
https://msdn.microsoft.com/de-de/library/windows/desktop/dd144941(v=vs.85).aspx – it can fail.

If the function fails, windows doesn’t fill the struct, which was given to GetTextMetrics and its values are kept uninitialized – so cairo went depending on a random effect into different parts of code afterwards (symbol fonts / non symbol fonts) and didn’t make a clean error.

Because the font, which fails for GetTextMetrics function, is from a customer document and I don’t have the right to provide the stuff to the outside, I cannot supply it to this list. But it is a reduced truetype font, which contains only a .notdef glyph and one additional glyph, which doesn’t have any contours, mapped to a space.

Question:
When Cairo fails internally for any reason it set sets an error code inside the context – and all content later, which i want to output on this context isn’t processed anymore. In above case it works, that I ignore that error-setting and process the rest of the document.
So how can I achieve, that when I left the erroneous state inside the context, that it works again? I miss something like a cairo_reset_error function.


Best regards,

Patrick

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Index: cairo-win32-font.c
===================================================================
--- cairo-win32-font.c	(revision 2201)
+++ cairo-win32-font.c	(revision 2202)
@@ -889,7 +889,7 @@
     cairo_status_t status;
     cairo_font_extents_t extents;
 
-    TEXTMETRIC metrics;
+	TEXTMETRIC metrics = {0};
     HDC hdc;
 
     hdc = _get_global_font_dc ();
@@ -902,8 +902,13 @@
 	status = cairo_win32_scaled_font_select_font (&scaled_font->base, hdc);
 	if (status)
 	    return status;
-	GetTextMetrics (hdc, &metrics);
+	if(!GetTextMetrics (hdc, &metrics))
+	{
+		status = _cairo_win32_print_gdi_error ("_cairo_win32_scaled_font_set_metrics:GetTextMetrics");
+	}
 	cairo_win32_scaled_font_done_font (&scaled_font->base);
+	if (status)
+		return status;
 
 	extents.ascent = metrics.tmAscent / scaled_font->logical_scale;
 	extents.descent = metrics.tmDescent / scaled_font->logical_scale;