On Thu, 16 Oct 2014 16:37:02 -0500
Derek Foreman <[email protected]> wrote:
> Pixman uses y-x banded rectangles to represent regions. We use these
> y-x banded rectangles to generate triangle fans, resulting in more
> geometry than strictly necessary to draw the screen.
>
> This patch combines the bands to reduce geometry for complex scenes.
> ---
> src/gl-renderer.c | 67
> ++++++++++++++++++++++++++++++++++++++++++++++++++++---
> 1 file changed, 64 insertions(+), 3 deletions(-)
>
> diff --git a/src/gl-renderer.c b/src/gl-renderer.c
> index 076c242..40447c7 100644
> --- a/src/gl-renderer.c
> +++ b/src/gl-renderer.c
> @@ -25,6 +25,7 @@
> #include <GLES2/gl2.h>
> #include <GLES2/gl2ext.h>
>
> +#include <stdbool.h>
> #include <stdlib.h>
> #include <string.h>
> #include <ctype.h>
> @@ -296,6 +297,55 @@ calculate_edges(struct weston_view *ev, pixman_box32_t
> *rect,
> return n;
> }
>
> +static bool
> +merge_down(pixman_box32_t *a, pixman_box32_t *b, pixman_box32_t *merge)
> +{
> + if (a->x1 == b->x1 && a->x2 == b->x2 && a->y1 == b->y2) {
> + merge->x1 = a->x1;
> + merge->x2 = a->x2;
> + merge->y1 = b->y1;
> + merge->y2 = a->y2;
> + return true;
> + }
> + return false;
> +}
> +
> +static int
> +compress_bands(pixman_box32_t *inrects, int nrects,
> + pixman_box32_t **outrects)
> +{
> + bool merged;
> + pixman_box32_t *out, merge_rect;
> + int i, j, nout;
> +
> + if (!nrects) {
> + *outrects = NULL;
> + return 0;
> + }
> +
> + /* nrects is an upper bound - we're not too worried about
> + * allocating a little extra
> + */
> + out = malloc(sizeof(pixman_box32_t) * nrects);
> + out[0] = inrects[0];
> + nout = 1;
> + for (i = 1; i < nrects; i++) {
> + for (j = 0; j < nout; j++) {
> + merged = merge_down(&inrects[i], &out[j], &merge_rect);
> + if (merged) {
> + out[j] = merge_rect;
> + break;
> + }
> + }
> + if (!merged) {
> + out[nout] = inrects[i];
> + nout++;
> + }
> + }
> + *outrects = out;
> + return nout;
> +}
> +
> static int
> texture_region(struct weston_view *ev, pixman_region32_t *region,
> pixman_region32_t *surf_region)
> @@ -306,11 +356,20 @@ texture_region(struct weston_view *ev,
> pixman_region32_t *region,
> GLfloat *v, inv_width, inv_height;
> unsigned int *vtxcnt, nvtx = 0;
> pixman_box32_t *rects, *surf_rects;
> - int i, j, k, nrects, nsurf;
> -
> - rects = pixman_region32_rectangles(region, &nrects);
> + pixman_box32_t *raw_rects;
> + int i, j, k, nrects, nsurf, raw_nrects;
> + bool used_band_compression;
> + raw_rects = pixman_region32_rectangles(region, &raw_nrects);
> surf_rects = pixman_region32_rectangles(surf_region, &nsurf);
>
> + if (raw_nrects < 4) {
> + used_band_compression = false;
> + nrects = raw_nrects;
> + rects = raw_rects;
> + } else {
> + nrects = compress_bands(raw_rects, raw_nrects, &rects);
> + used_band_compression = true;
> + }
> /* worst case we can have 8 vertices per rect (ie. clipped into
> * an octagon):
> */
> @@ -369,6 +428,8 @@ texture_region(struct weston_view *ev, pixman_region32_t
> *region,
> }
> }
>
> + if (used_band_compression)
> + free(rects);
> return nvtx;
> }
>
Hi Derek,
could you explain a bit where I can see the effect of this and how
big an improvement it is?
Thanks,
pq
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