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Simply the matrix calculation for zooming

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In order to apply the zoom transformation to the output matrix, Weston was
doing the following:

• Create a temporary matrix to hold the translation
• Invert the translation matrix using weston_matrix_invert into
  another temporary matrix
• Scale that matrix by the scale factor
• Multiply the current matrix with the temporary matrix

Using weston_matrix_invert to invert a translation matrix is over the top.
Instead we can just negate the values we pass to weston_matrix_translate.
Matrix multiplication is associative so creating a temporary matrix to hold the
scale and translation transform should be equivalent to just applying them
directly to the output matrix.
This commit is contained in:
Neil Roberts
2014-04-25 13:19:37 +01:00
committed by Kristian Høgsberg
parent a69dc01a6e
commit 1e40a7ec7a
1 changed files with 4 additions and 9 deletions
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src/compositor.c
+4 -9
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@@ -3188,8 +3188,6 @@ WL_EXPORT void
weston_output_update_matrix(struct weston_output *output)
{
float magnification;
struct weston_matrix camera;
struct weston_matrix modelview;
weston_matrix_init(&output->matrix);
weston_matrix_translate(&output->matrix,
@@ -3204,14 +3202,11 @@ weston_output_update_matrix(struct weston_output *output)
if (output->zoom.active) {
magnification = 1 / (1 - output->zoom.spring_z.current);
weston_matrix_init(&camera);
weston_matrix_init(&modelview);
weston_output_update_zoom(output);
weston_matrix_translate(&camera, output->zoom.trans_x,
-output->zoom.trans_y, 0);
weston_matrix_invert(&modelview, &camera);
weston_matrix_scale(&modelview, magnification, magnification, 1.0);
weston_matrix_multiply(&output->matrix, &modelview);
weston_matrix_translate(&output->matrix, -output->zoom.trans_x,
output->zoom.trans_y, 0);
weston_matrix_scale(&output->matrix, magnification,
magnification, 1.0);
}
output->dirty = 0;