diff options
Diffstat (limited to 'src/mesa')
| -rw-r--r-- | src/mesa/swrast/s_zoom.c | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/src/mesa/swrast/s_zoom.c b/src/mesa/swrast/s_zoom.c index 1fac7498aa8..0908265fe9d 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; } |