Re: PDF: Font size is rounded

Adrian Johnson <[email protected]>
Newsgroups gmane.comp.lib.cairo
Message-ID <[email protected]> 
I found a problem with my previous patch when testing. I have rewritten
the patch, created a test case, and tested it with the test suite. The
attached patch is the fix I will push out if there are no objections.

A branch including the test case and ref images is at:

https://cgit.freedesktop.org/~ajohnson/cairo/log/?h=unhinted-metrics


On 16/04/16 22:36, Kouhei Sutou wrote:
> Hi,
> 
> In <[email protected]>
>   "Re: [cairo] PDF: Font size is rounded" on Sat, 2 Apr 2016 14:16:27 +1030,
>   Adrian Johnson <[email protected]> wrote:
> 
>> I put some printfs in _cairo_ft_scaled_glyph_init (in cairo-ft-font.c).
>> It appears that FreeType is returning hinted metrics. I'm guessing that
>> to get unhinted metrics of TrueType fonts we need to set the scale to
>> the EM size like we do for win32 fonts.
>>
>> I'm attaching a patch to do this. It fixes your test case. I don't know
>> if this patch is the correct way to fix the problem. I am not familiar
>> with the FreeType font backend.
> 
> Could someone who know about the FreeType font backend
> review the patch and commit the patch to the cairo
> repository? I confirmed that the patch fixes the problem I
> reported. I want the next cairo release to include this
> patch.
> 
> 
> Thanks,
> --
> kou
>

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0001-ft-set-font-size-to-em-size-when-retrieving-unhinted.patch (text/x-patch, 6.7 KB) 
From 1179a21d879f1fcee5c2cae5752e63506e7ce288 Mon Sep 17 00:00:00 2001
From: Adrian Johnson <[email protected]>
Date: Sat, 18 Jun 2016 13:16:57 +0930
Subject: [PATCH] ft: set font size to em size when retrieving unhinted metrics

fixes text-unhinted-metrics test
---
 src/cairo-ft-font.c | 140 +++++++++++++++++++++++++++++++++-------------------
 1 file changed, 90 insertions(+), 50 deletions(-)

diff --git a/src/cairo-ft-font.c b/src/cairo-ft-font.c
index a0c7beb..4f31304 100644
--- a/src/cairo-ft-font.c
+++ b/src/cairo-ft-font.c
@@ -2209,6 +2209,55 @@ _cairo_ft_scaled_glyph_vertical_layout_bearing_fix (void        *abstract_font,
 }
 
 static cairo_int_status_t
+_cairo_ft_scaled_glyph_load_glyph (cairo_ft_scaled_font_t *scaled_font,
+				   cairo_scaled_glyph_t   *scaled_glyph,
+				   FT_Face                 face,
+				   int                     load_flags,
+				   cairo_bool_t            use_em_size,
+				   cairo_bool_t            vertical_layout)
+{
+    FT_Error error;
+    cairo_status_t status;
+
+    if (use_em_size) {
+	cairo_matrix_t em_size;
+	cairo_matrix_init_scale (&em_size, face->units_per_EM, face->units_per_EM);
+	status = _cairo_ft_unscaled_font_set_scale (scaled_font->unscaled, &em_size);
+    } else {
+	status = _cairo_ft_unscaled_font_set_scale (scaled_font->unscaled,
+						    &scaled_font->base.scale);
+    }
+    if (unlikely (status))
+	return status;
+
+    error = FT_Load_Glyph (face,
+			   _cairo_scaled_glyph_index(scaled_glyph),
+			   load_flags);
+    /* XXX ignoring all other errors for now.  They are not fatal, typically
+     * just a glyph-not-found. */
+    if (error == FT_Err_Out_Of_Memory)
+	return  _cairo_error (CAIRO_STATUS_NO_MEMORY);
+
+    /*
+     * synthesize glyphs if requested
+     */
+#if HAVE_FT_GLYPHSLOT_EMBOLDEN
+    if (scaled_font->ft_options.synth_flags & CAIRO_FT_SYNTHESIZE_BOLD)
+	FT_GlyphSlot_Embolden (face->glyph);
+#endif
+
+#if HAVE_FT_GLYPHSLOT_OBLIQUE
+    if (scaled_font->ft_options.synth_flags & CAIRO_FT_SYNTHESIZE_OBLIQUE)
+	FT_GlyphSlot_Oblique (face->glyph);
+#endif
+
+    if (vertical_layout)
+	_cairo_ft_scaled_glyph_vertical_layout_bearing_fix (scaled_font, face->glyph);
+
+    return CAIRO_STATUS_SUCCESS;
+}
+
+static cairo_int_status_t
 _cairo_ft_scaled_glyph_init (void			*abstract_font,
 			     cairo_scaled_glyph_t	*scaled_glyph,
 			     cairo_scaled_glyph_info_t	 info)
@@ -2218,22 +2267,17 @@ _cairo_ft_scaled_glyph_init (void			*abstract_font,
     cairo_ft_unscaled_font_t *unscaled = scaled_font->unscaled;
     FT_GlyphSlot glyph;
     FT_Face face;
-    FT_Error error;
     int load_flags = scaled_font->ft_options.load_flags;
     FT_Glyph_Metrics *metrics;
     double x_factor, y_factor;
     cairo_bool_t vertical_layout = FALSE;
     cairo_status_t status;
+    cairo_bool_t scaled_glyph_loaded = FALSE;
 
     face = _cairo_ft_unscaled_font_lock_face (unscaled);
     if (!face)
 	return _cairo_error (CAIRO_STATUS_NO_MEMORY);
 
-    status = _cairo_ft_unscaled_font_set_scale (scaled_font->unscaled,
-				                &scaled_font->base.scale);
-    if (unlikely (status))
-	goto FAIL;
-
     /* Ignore global advance unconditionally */
     load_flags |= FT_LOAD_IGNORE_GLOBAL_ADVANCE_WIDTH;
 
@@ -2264,37 +2308,23 @@ _cairo_ft_scaled_glyph_init (void			*abstract_font,
     /* load_flags |= FT_LOAD_COLOR; */
 #endif
 
-    error = FT_Load_Glyph (face,
-			   _cairo_scaled_glyph_index(scaled_glyph),
-			   load_flags);
-    /* XXX ignoring all other errors for now.  They are not fatal, typically
-     * just a glyph-not-found. */
-    if (error == FT_Err_Out_Of_Memory) {
-	status = _cairo_error (CAIRO_STATUS_NO_MEMORY);
-	goto FAIL;
-    }
-
-    glyph = face->glyph;
 
-    /*
-     * synthesize glyphs if requested
-     */
-#if HAVE_FT_GLYPHSLOT_EMBOLDEN
-    if (scaled_font->ft_options.synth_flags & CAIRO_FT_SYNTHESIZE_BOLD)
-	FT_GlyphSlot_Embolden (glyph);
-#endif
+    if (info & CAIRO_SCALED_GLYPH_INFO_METRICS) {
 
-#if HAVE_FT_GLYPHSLOT_OBLIQUE
-    if (scaled_font->ft_options.synth_flags & CAIRO_FT_SYNTHESIZE_OBLIQUE)
-	FT_GlyphSlot_Oblique (glyph);
-#endif
+	cairo_bool_t hint_metrics = scaled_font->base.options.hint_metrics != CAIRO_HINT_METRICS_OFF;
 
-    if (vertical_layout)
-	_cairo_ft_scaled_glyph_vertical_layout_bearing_fix (scaled_font, glyph);
+	status = _cairo_ft_scaled_glyph_load_glyph (scaled_font,
+						    scaled_glyph,
+						    face,
+						    load_flags,
+						    !hint_metrics,
+						    vertical_layout);
+	if (unlikely (status))
+	    goto FAIL;
 
-    if (info & CAIRO_SCALED_GLYPH_INFO_METRICS) {
+	glyph = face->glyph;
+	scaled_glyph_loaded = hint_metrics;
 
-	cairo_bool_t hint_metrics = scaled_font->base.options.hint_metrics != CAIRO_HINT_METRICS_OFF;
 	/*
 	 * Compute font-space metrics
 	 */
@@ -2392,6 +2422,20 @@ _cairo_ft_scaled_glyph_init (void			*abstract_font,
     if ((info & CAIRO_SCALED_GLYPH_INFO_SURFACE) != 0) {
 	cairo_image_surface_t	*surface;
 
+	if (!scaled_glyph_loaded) {
+	    status = _cairo_ft_scaled_glyph_load_glyph (scaled_font,
+							scaled_glyph,
+							face,
+							load_flags,
+							FALSE,
+							vertical_layout);
+	    if (unlikely (status))
+		goto FAIL;
+
+	    glyph = face->glyph;
+	    scaled_glyph_loaded = TRUE;
+	}
+
 	if (glyph->format == FT_GLYPH_FORMAT_OUTLINE) {
 	    status = _render_glyph_outline (face, &scaled_font->ft_options.base,
 					    &surface);
@@ -2423,27 +2467,23 @@ _cairo_ft_scaled_glyph_init (void			*abstract_font,
 	 * so reload it. This will probably never occur though
 	 */
 	if ((info & CAIRO_SCALED_GLYPH_INFO_SURFACE) != 0) {
-	    error = FT_Load_Glyph (face,
-				   _cairo_scaled_glyph_index(scaled_glyph),
-				   load_flags | FT_LOAD_NO_BITMAP);
-	    /* XXX ignoring all other errors for now.  They are not fatal, typically
-	     * just a glyph-not-found. */
-	    if (error == FT_Err_Out_Of_Memory) {
-		status = _cairo_error (CAIRO_STATUS_NO_MEMORY);
+	    scaled_glyph_loaded = FALSE;
+	    load_flags |= FT_LOAD_NO_BITMAP;
+	}
+
+	if (!scaled_glyph_loaded) {
+	    status = _cairo_ft_scaled_glyph_load_glyph (scaled_font,
+							scaled_glyph,
+							face,
+							load_flags,
+							FALSE,
+							vertical_layout);
+	    if (unlikely (status))
 		goto FAIL;
-	    }
-#if HAVE_FT_GLYPHSLOT_EMBOLDEN
-	    if (scaled_font->ft_options.synth_flags & CAIRO_FT_SYNTHESIZE_BOLD)
-		FT_GlyphSlot_Embolden (glyph);
-#endif
-#if HAVE_FT_GLYPHSLOT_OBLIQUE
-	    if (scaled_font->ft_options.synth_flags & CAIRO_FT_SYNTHESIZE_OBLIQUE)
-		FT_GlyphSlot_Oblique (glyph);
-#endif
-	    if (vertical_layout)
-		_cairo_ft_scaled_glyph_vertical_layout_bearing_fix (scaled_font, glyph);
 
+	    glyph = face->glyph;
 	}
+
 	if (glyph->format == FT_GLYPH_FORMAT_OUTLINE)
 	    status = _decompose_glyph_outline (face, &scaled_font->ft_options.base,
 					       &path);
-- 
2.1.4
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