fbsplash: limit progress bar flicker

Progress bar updates flicker quite a bit on slow hw / high resolutions
as the background is completely cleared before the new progress bar
position is drawn on top.

Improve it by first drawing the progress bar and then only fill the
remaining rows with the background.

function                                             old     new   delta
fb_drawprogressbar                                   444     429     -15

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 19 insertions, 11 deletions

diff --git a/miscutils/fbsplash.c b/miscutils/fbsplash.c
index 51ba4729e..bc9ac8fe1 100644
--- a/miscutils/fbsplash.c
+++ b/miscutils/fbsplash.c
@@ -213,14 +213,15 @@ static void fb_drawfullrectangle(int nx1pos, int ny1pos, int nx2pos, int ny2pos,
  */
 static void fb_drawprogressbar(unsigned percent)
 {
-        int i, left_x, top_y, width, height;
+        int left_x, top_y, pos_x;
+        unsigned width, height;
 
         // outer box
         left_x = G.nbar_posx;
         top_y = G.nbar_posy;
         width = G.nbar_width - 1;
         height = G.nbar_height - 1;
-        if ((height | width) < 0)
+        if ((int)(height | width) < 0)
                 return;
         // NB: "width" of 1 actually makes rect with width of 2!
         fb_drawrectangle();
@@ -230,30 +231,37 @@ static void fb_drawprogressbar(unsigned percent)
         top_y++;
         width -= 2;
         height -= 2;
-        if ((height | width) < 0)
+        if ((int)(height | width) < 0)
                 return;
-        fb_drawfullrectangle(
-                        left_x, top_y,
-                                        left_x + width, top_y + height,
-                        G.nbar_colr, G.nbar_colg, G.nbar_colb);
 
+        pos_x = left_x;
         if (percent > 0) {
+                int y;
+                unsigned i;
+
                 // actual progress bar
-                width = width * percent / 100;
+                pos_x += (unsigned)(width * percent) / 100;
+
+                y = top_y;
                 i = height;
                 if (height == 0)
                         height++; // divide by 0 is bad
                 while (i >= 0) {
                         // draw one-line thick "rectangle"
                         // top line will have gray lvl 200, bottom one 100
-                        unsigned gray_level = 100 + i*100/height;
+                        unsigned gray_level = 100 + i*100 / height;
                         fb_drawfullrectangle(
-                                        left_x, top_y, left_x + width, top_y,
+                                        left_x, y, pos_x, y,
                                         gray_level, gray_level, gray_level);
-                        top_y++;
+                        y++;
                         i--;
                 }
         }
+
+        fb_drawfullrectangle(
+                        pos_x, top_y,
+                        left_x + width, top_y + height,
+                        G.nbar_colr, G.nbar_colg, G.nbar_colb);
 }