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authorBrian <brian@yutani.localnet.net>2007-04-14 07:49:21 -0600
committerBrian <brian@yutani.localnet.net>2007-04-14 07:49:21 -0600
commite19cfabb6ec091982cc92ec59aa5dedf3cdf2302 (patch)
treeffb836d7340ff8309ec3270bfbbe995afa9507e6 /src/mesa/swrast
parent8d8a3cc39816168e5f04a668ae184cafe64d4fd2 (diff)
fix negative zoom factor bug (10636), more comments
Diffstat (limited to 'src/mesa/swrast')
-rw-r--r--src/mesa/swrast/s_zoom.c14
1 files changed, 11 insertions, 3 deletions
diff --git a/src/mesa/swrast/s_zoom.c b/src/mesa/swrast/s_zoom.c
index 1fac7498aa..0908265fe9 100644
--- a/src/mesa/swrast/s_zoom.c
+++ b/src/mesa/swrast/s_zoom.c
@@ -37,8 +37,9 @@
* Compute the bounds of the region resulting from zooming a pixel span.
* The resulting region will be entirely inside the window/scissor bounds
* so no additional clipping is needed.
- * \param imageX, imageY position of the overall image being drawn
+ * \param imageX, imageY position of the mage being drawn (gl WindowPos)
* \param spanX, spanY position of span being drawing
+ * \param width number of pixels in span
* \param x0, x1 returned X bounds of zoomed region [x0, x1)
* \param y0, y1 returned Y bounds of zoomed region [y0, y1)
* \return GL_TRUE if any zoomed pixels visible, GL_FALSE if totally clipped
@@ -98,7 +99,11 @@ compute_zoomed_bounds(GLcontext *ctx, GLint imageX, GLint imageY,
/**
- * Can use this for unzooming X or Y values.
+ * Convert a zoomed x image coordinate back to an unzoomed x coord.
+ * 'zx' is screen position of a pixel in the zoomed image, who's left edge
+ * is at 'imageX'.
+ * return corresponding x coord in the original, unzoomed image.
+ * This can use this for unzooming X or Y values.
*/
static INLINE GLint
unzoom_x(GLfloat zoomX, GLint imageX, GLint zx)
@@ -108,7 +113,10 @@ unzoom_x(GLfloat zoomX, GLint imageX, GLint zx)
zx - imageX = (x - imageX) * zoomX;
(zx - imageX) / zoomX = x - imageX;
*/
- GLint x = imageX + (GLint) ((zx - imageX) / zoomX);
+ GLint x;
+ if (zoomX < 0.0)
+ zx++;
+ x = imageX + (GLint) ((zx - imageX) / zoomX);
return x;
}