Bug#448555: fonts are not hinted, therefore blurry and ugly

[Samuel Rødal <sroedal@trolltech.com>]

Fathi Boudra wrote:
> Hi,
>
>
> > This will be fixed in Qt 4.5.1 (ref
> > http://www.qtsoftware.com/developer/task-tracker/index_html?method=entry&id=248387).
>
> > In conclusion I hope you do not include the proposed patch in Debian or in
> > qt-copy :)
>
> thanks for your reply.
>
> Qt snapshots aren't updated since 2-3 weeks.
> Is it possible to get the patch now and apply it to qt-copy ?
>
> cheers,
>
> Fathi

Sure, I've attached the patch to this mail.

Note that to enable the legacy LCD filtering you need to edit your 
fonts.conf settings (http://fontconfig.org/fontconfig-user.html). It 
should contain the snippet mentioned in this qt-interest post:

http://article.gmane.org/gmane.comp.lib.qt.general/11465

There is currently a bug in Cairo that causes it to use Legacy LCD 
filtering by default (ref the discussion at 
http://bugs.freedesktop.org/show_bug.cgi?id=10301). Thus, if you want Qt 
applications to look like GTK applications you need to manually set the 
LCD filtering method to Legacy as described in the qt-interest post above.

Cheers,
Samuel

>From b7f4094bcb9eccfb14c5b1f1e6502a4b11c78047 Mon Sep 17 00:00:00 2001
From: =?utf-8?q?Samuel=20R=C3=B8dal?= <sroedal@trolltech.com>
Date: Mon, 16 Mar 2009 14:26:22 +0100
Subject: [PATCH] X11: Use legacy LCD filtering if specified in font config.

If Freetype is built without subpixel rendering, we should use
the Qt 3 intrapixel filter instead of the bitmap convolution
when the Legacy LCD filter is chosen.

Task-number: 248387
Reviewed-by: Jens
---
 src/gui/text/qfontengine_ft.cpp |   28 ++++++++++++++++++++++------
 1 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/src/gui/text/qfontengine_ft.cpp b/src/gui/text/qfontengine_ft.cpp
index 264d8de..f2389e3 100644
--- a/src/gui/text/qfontengine_ft.cpp
+++ b/src/gui/text/qfontengine_ft.cpp
@@ -529,7 +529,7 @@ static const uint subpixel_filter[3][3] = {
 };
 #endif
 
-static void convertRGBToARGB(const uchar *src, uint *dst, int width, int height, int src_pitch, bool bgr)
+static void convertRGBToARGB(const uchar *src, uint *dst, int width, int height, int src_pitch, bool bgr, bool legacyFilter)
 {
     int h = height;
     const int offs = bgr ? -1 : 1;
@@ -540,8 +540,16 @@ static void convertRGBToARGB(const uchar *src, uint *dst, int width, int height,
             uint red = src[x+1-offs];
             uint green = src[x+1];
             uint blue = src[x+1+offs];
-            uint alpha = green;
-            uint res = (alpha << 24) + (red << 16) + (green << 8) + blue;
+            uint res;
+#if !defined(QT_USE_FREETYPE_LCDFILTER)
+            if (legacyFilter) {
+                uint high = (red*subpixel_filter[0][0] + green*subpixel_filter[0][1] + blue*subpixel_filter[0][2]) >> 8;
+                uint mid = (red*subpixel_filter[1][0] + green*subpixel_filter[1][1] + blue*subpixel_filter[1][2]) >> 8;
+                uint low = (red*subpixel_filter[2][0] + green*subpixel_filter[2][1] + blue*subpixel_filter[2][2]) >> 8;
+                res = (mid << 24) + (high << 16) + (mid << 8) + low;
+            } else
+#endif
+            res = (green << 24) + (red << 16) + (green << 8) + blue;
             *dd = res;
             ++dd;
         }
@@ -941,7 +949,7 @@ QFontEngineFT::Glyph *QFontEngineFT::loadGlyph(QGlyphSet *set, uint glyph, Glyph
         glyph_buffer = new uchar[glyph_buffer_size];
 
         if (hsubpixel)
-            convertRGBToARGB(slot->bitmap.buffer, (uint *)glyph_buffer, info.width, info.height, slot->bitmap.pitch, subpixelType != QFontEngineFT::Subpixel_RGB);
+            convertRGBToARGB(slot->bitmap.buffer, (uint *)glyph_buffer, info.width, info.height, slot->bitmap.pitch, subpixelType != QFontEngineFT::Subpixel_RGB, false);
         else if (vfactor != 1)
             convertRGBToARGB_V(slot->bitmap.buffer, (uint *)glyph_buffer, info.width, info.height, slot->bitmap.pitch, subpixelType != QFontEngineFT::Subpixel_VRGB);
     } else
@@ -1042,8 +1050,16 @@ QFontEngineFT::Glyph *QFontEngineFT::loadGlyph(QGlyphSet *set, uint glyph, Glyph
             Q_ASSERT (bitmap.pixel_mode == FT_PIXEL_MODE_GRAY);
             Q_ASSERT(antialias);
             uchar *convoluted = new uchar[bitmap.rows*bitmap.pitch];
-            convoluteBitmap(bitmap.buffer, convoluted, bitmap.width, info.height, bitmap.pitch);
-            convertRGBToARGB(convoluted + 1, (uint *)glyph_buffer, info.width, info.height, bitmap.pitch, subpixelType != QFontEngineFT::Subpixel_RGB);
+            bool useLegacyLcdFilter = false;
+#if defined(FT_LCD_FILTER_H)
+            useLegacyLcdFilter = (lcdFilterType == FT_LCD_FILTER_LEGACY);
+#endif
+            uchar *buffer = bitmap.buffer;
+            if (!useLegacyLcdFilter) {
+                convoluteBitmap(bitmap.buffer, convoluted, bitmap.width, info.height, bitmap.pitch);
+                buffer = convoluted;
+            }
+            convertRGBToARGB(buffer + 1, (uint *)glyph_buffer, info.width, info.height, bitmap.pitch, subpixelType != QFontEngineFT::Subpixel_RGB, useLegacyLcdFilter);
             delete [] convoluted;
         } else if (vfactor != 1) {
             convertRGBToARGB_V(bitmap.buffer, (uint *)glyph_buffer, info.width, info.height, bitmap.pitch, subpixelType != QFontEngineFT::Subpixel_VRGB);
-- 
1.6.2