Archives/OpenTTD-patches
2
0
Fork 0
mirror of https://github.com/JGRennison/OpenTTD-patches.git synced 2024-11-11 13:10:45 +00:00
Code Issues Packages Projects Releases Wiki Activity

(svn r27322) -Fix: Clipping of inclined lines did not account for the 'horizontal width' being bigger than the 'real width'. (adf88)

Browse Source
This commit is contained in:
frosch 2015-06-28 15:50:13 +00:00
parent bddcd33ed7
commit a65a194416
1 changed files with 13 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
src/gfx.cpp
View File

@ -195,20 +195,26 @@ static inline void GfxDoDrawLine(void *video, int x, int y, int x2, int y2, int
int grade_y = y2 - y;
int grade_x = x2 - x;
/* Clipping rectangle. Slightly extended so we can ignore the width of the line. */
uint extra = CeilDiv(3 * width, 4); // not less then "width * sqrt(2) / 2"
Rect clip = { -extra, -extra, screen_width - 1 + extra, screen_height - 1 + extra };
/* prevent integer overflows. */
int margin = 1;
while (INT_MAX / abs(grade_y) < max(abs(x), abs(screen_width - x))) {
while (INT_MAX / abs(grade_y) < max(abs(clip.left - x), abs(clip.right - x))) {
grade_y /= 2;
grade_x /= 2;
margin *= 2; // account for rounding errors
}
/* If the line is outside the screen on the same side at X positions 0
* and screen_width, we don't need to draw anything. */
int offset_0 = y - x * grade_y / grade_x;
int offset_width = y + (screen_width - x) * grade_y / grade_x;
if ((offset_0 > screen_height + width / 2 + margin && offset_width > screen_height + width / 2 + margin) ||
(offset_0 < -width / 2 - margin && offset_width < -width / 2 - margin)) {
/* Imagine that the line is infinitely long and it intersects with
* infinitely long left and right edges of the clipping rectangle.
* If booth intersection points are outside the clipping rectangle
* and booth on the same side of it, we don't need to draw anything. */
int left_isec_y = y + (clip.left - x) * grade_y / grade_x;
int right_isec_y = y + (clip.right - x) * grade_y / grade_x;
if ((left_isec_y > clip.bottom + margin && right_isec_y > clip.bottom + margin) ||
(left_isec_y < clip.top - margin && right_isec_y < clip.top - margin)) {
return;
}