shithub: choc

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textscreen: Fix jump when clicking on scrollbars.

Clicking on a scrollbar should scroll the cursor to that location, but
the logic for it was buggy because of loss of precision when doing an
integer divide. When dividing by bar_max, seek up to the nearest value
so that the cursor always arrives where we clicked.

Thanks to Alexandre-Xavier for reporting this bug. This fixes #359.

--- a/textscreen/txt_scrollpane.c

+++ b/textscreen/txt_scrollpane.c

@@ -487,7 +487,7 @@

             int range = FullWidth(scrollpane) - scrollpane->w;

             int bar_max = scrollpane->w - 3;

-            scrollpane->x = ((rel_x - 1) * range + (bar_max / 2)) / bar_max;

+            scrollpane->x = ((rel_x - 1) * range + bar_max - 1) / bar_max;

         }

         return;

@@ -509,7 +509,7 @@

             int range = FullHeight(scrollpane) - scrollpane->h;

             int bar_max = scrollpane->h - 3;

-            scrollpane->y = ((rel_y - 1) * range + (bar_max / 2)) / bar_max;

+            scrollpane->y = ((rel_y - 1) * range + bar_max - 1) / bar_max;

         }

         return;