[AD] character clipping proposal

[deleveld@xxxxxxxxxx]

Hi everyone,

I noticed that text output in Allegro doesn't consider clipping  
conditions and renders each character of the string even when it can  
be easily determined that characters will be fully clipped.

Here is a patch on 4.2.2 that incorporates character based clipping to  
mono_render and color_render.  The unclipped rendering speed is not  
slowed down by any detectable amount but the clipped drawing speed is  
quite a bit faster.  It's hard to say exactly how much faster since  
test.exe chooses different clipping conditions all the time and  
profiling doesnt(?) check drawing with clipping.

The patch is very simple and should be easily translatable to WIP  
versions.  I cant test them because the WIP versions dont compile for  
me.

best regards,

Doug eleveld

diff -wur allegro/src/font.c deleveld_charclip_patch/src/font.c
--- allegro/src/font.c	2006-12-11 19:14:36 +0000
+++ deleveld_charclip_patch/src/font.c	2008-05-14 16:32:50 +0000
@@ -540,10 +540,18 @@
     int ch = 0;
     AL_CONST char* p = text;
 
+    if (bmp->clip) {
+        if (x >= bmp->cr || y >= bmp->cb || y + text_height(f) <= bmp->ct)
+            return;
+    }
+
     acquire_bitmap(bmp);
 
     while( (ch = ugetxc(&p)) ) {
         x += f->vtable->render_char(f, ch, fg, bg, bmp, x, y);
+
+        if (bmp->clip && x >= bmp->cr)
+             break;
     }
 
     release_bitmap(bmp);
@@ -995,6 +1003,11 @@
     AL_CONST char* p = text;
     int ch = 0;
 
+    if (bmp->clip) {
+        if (x >= bmp->cr || y >= bmp->cb || y + text_height(f) <= bmp->ct)
+            return;
+    }
+
     acquire_bitmap(bmp);
 
     if(fg < 0 && bg >= 0) {
@@ -1004,6 +1017,9 @@
 
     while( (ch = ugetxc(&p)) ) {
         x += f->vtable->render_char(f, ch, fg, bg, bmp, x, y);
+
+        if (bmp->clip && x >= bmp->cr)
+            break;
     }
 
     release_bitmap(bmp);