[PATCH weston v2 2/2] cairo-util: fix shadows for small clients

[Pekka Paalanen]

On Wed, 29 Oct 2014 14:51:23 +0100
Marek Chalupa <mchqwerty at gmail.com> wrote:

> If the client is small (< 128 pixels in any ward),
> then the shadows overlap and create dark lines behind clients.
> This is a problem mosly with pop-up menues. The lines become observable
> when the menu has less than three items. The other case is when
> the client doesn't restrict its size when resizing (try
> 'weston-eventdemo --max-width=1 --max-height=1' for example)
> 
> This fixes a part of the bug:
> https://bugs.freedesktop.org/show_bug.cgi?id=78511
> 
> v2:
>   - rework computing of the size of corners
>   - rewrite some comments
>   - rename tile_mask to render_shadow (in separate patch)
> 
> Signed-off-by: Marek Chalupa <mchqwerty at gmail.com>
> ---
>  shared/cairo-util.c | 129 +++++++++++++++++++++++++++++++++-------------------
>  1 file changed, 83 insertions(+), 46 deletions(-)
> 
> diff --git a/shared/cairo-util.c b/shared/cairo-util.c
> index 73e3ae7..a73c08b 100644
> --- a/shared/cairo-util.c
> +++ b/shared/cairo-util.c
> @@ -142,7 +142,7 @@ render_shadow(cairo_t *cr, cairo_surface_t *surface,
>  {
>  	cairo_pattern_t *pattern;
>  	cairo_matrix_t matrix;
> -	int i, fx, fy, vmargin;
> +	int i, fx, fy, shadow_height, shadow_width;
>  
>  	cairo_set_source_rgba(cr, 0, 0, 0, 0.45);
>  	cairo_set_operator(cr, CAIRO_OPERATOR_OVER);
> @@ -150,6 +150,14 @@ render_shadow(cairo_t *cr, cairo_surface_t *surface,
>  	cairo_pattern_set_filter(pattern, CAIRO_FILTER_NEAREST);
>  
>  	for (i = 0; i < 4; i++) {
> +		/* when fy is set, then we are working with lower corners,
> +		 * when fx is set, then we are working with right corners
> +		 *
> +		 *  00 ------- 01
> +		 *   |         |
> +		 *   |         |
> +		 *  10 ------- 11
> +		 */
>  		fx = i & 1;
>  		fy = i >> 1;
>  
> @@ -158,63 +166,92 @@ render_shadow(cairo_t *cr, cairo_surface_t *surface,
>  					    -y + fy * (128 - height));
>  		cairo_pattern_set_matrix(pattern, &matrix);
>  
> -		if (fy)
> -			vmargin = margin;
> -		else
> -			vmargin = top_margin;
> +		shadow_width = margin;
> +		shadow_height = fy ? margin : top_margin;
> +
> +		/* if the shadows together are greater than the surface, we need
> +		 * to fix it - set the shadow size to the half of
> +		 * the size of surface. Also handle the case when the size is
> +		 * not divisible by 2. In that case we need one part of the
> +		 * shadow to be one pixel greater. !fy or !fx, respectively,
> +		 * will do the work.
> +		 */
> +		if (height < 2 * shadow_height)
> +			shadow_height = (height + !fy) / 2;
> +
> +		if (width < 2 * shadow_width)
> +			shadow_width = (width + !fx) / 2;
>  
>  		cairo_reset_clip(cr);
>  		cairo_rectangle(cr,
> -				x + fx * (width - margin),
> -				y + fy * (height - vmargin),
> -				margin, vmargin);
> +				x + fx * (width - shadow_width),
> +				y + fy * (height - shadow_height),
> +				shadow_width, shadow_height);
>  		cairo_clip (cr);
>  		cairo_mask(cr, pattern);
>  	}
>  
> -	/* Top stretch */
> -	cairo_matrix_init_translate(&matrix, 60, 0);
> -	cairo_matrix_scale(&matrix, 8.0 / width, 1);
> -	cairo_matrix_translate(&matrix, -x - width / 2, -y);
> -	cairo_pattern_set_matrix(pattern, &matrix);
> -	cairo_rectangle(cr, x + margin, y, width - 2 * margin, margin);
>  
> -	cairo_reset_clip(cr);
> -	cairo_rectangle(cr,
> -			x + margin,
> -			y,
> -			width - 2 * margin, margin);
> -	cairo_clip (cr);
> -	cairo_mask(cr, pattern);
> +	shadow_width = width - 2 * margin;
> +	shadow_height = top_margin;
> +	if (height < 2 * shadow_height)
> +		shadow_height = height / 2;
>  
> -	/* Bottom stretch */
> -	cairo_matrix_translate(&matrix, 0, -height + 128);
> -	cairo_pattern_set_matrix(pattern, &matrix);
> +	if (shadow_width > 0 && shadow_height) {
> +		/* Top stretch */
> +		cairo_matrix_init_translate(&matrix, 60, 0);
> +		cairo_matrix_scale(&matrix, 8.0 / width, 1);
> +		cairo_matrix_translate(&matrix, -x - width / 2, -y);
> +		cairo_pattern_set_matrix(pattern, &matrix);
> +		cairo_rectangle(cr, x + margin, y, shadow_width, shadow_height);
>  
> -	cairo_reset_clip(cr);
> -	cairo_rectangle(cr, x + margin, y + height - margin,
> -			width - 2 * margin, margin);
> -	cairo_clip (cr);
> -	cairo_mask(cr, pattern);
> +		cairo_reset_clip(cr);
> +		cairo_rectangle(cr,
> +				x + margin, y,
> +				shadow_width, shadow_height);
> +		cairo_clip (cr);
> +		cairo_mask(cr, pattern);
>  
> -	/* Left stretch */
> -	cairo_matrix_init_translate(&matrix, 0, 60);
> -	cairo_matrix_scale(&matrix, 1, 8.0 / height);
> -	cairo_matrix_translate(&matrix, -x, -y - height / 2);
> -	cairo_pattern_set_matrix(pattern, &matrix);
> -	cairo_reset_clip(cr);
> -	cairo_rectangle(cr, x, y + margin, margin, height - 2 * margin);
> -	cairo_clip (cr);
> -	cairo_mask(cr, pattern);
> +		/* Bottom stretch */
> +		cairo_matrix_translate(&matrix, 0, -height + 128);
> +		cairo_pattern_set_matrix(pattern, &matrix);
>  
> -	/* Right stretch */
> -	cairo_matrix_translate(&matrix, -width + 128, 0);
> -	cairo_pattern_set_matrix(pattern, &matrix);
> -	cairo_rectangle(cr, x + width - margin, y + margin,
> -			margin, height - 2 * margin);
> -	cairo_reset_clip(cr);
> -	cairo_clip (cr);
> -	cairo_mask(cr, pattern);
> +		cairo_reset_clip(cr);
> +		cairo_rectangle(cr, x + margin, y + height - margin,
> +				shadow_width, margin);
> +		cairo_clip (cr);
> +		cairo_mask(cr, pattern);
> +	}
> +
> +	shadow_width = margin;
> +	if (width < 2 * shadow_width)
> +		shadow_width = width / 2;
> +
> +	shadow_height = height - margin - top_margin;
> +
> +	/* if height is smaller than sum of margins,
> +	 * then the shadow is already done by the corners */
> +	if (shadow_height > 0 && shadow_width) {
> +		/* Left stretch */
> +		cairo_matrix_init_translate(&matrix, 0, 60);
> +		cairo_matrix_scale(&matrix, 1, 8.0 / height);
> +		cairo_matrix_translate(&matrix, -x, -y - height / 2);
> +		cairo_pattern_set_matrix(pattern, &matrix);
> +		cairo_reset_clip(cr);
> +		cairo_rectangle(cr, x, y + top_margin,
> +				shadow_width, shadow_height);
> +		cairo_clip (cr);
> +		cairo_mask(cr, pattern);
> +
> +		/* Right stretch */
> +		cairo_matrix_translate(&matrix, -width + 128, 0);
> +		cairo_pattern_set_matrix(pattern, &matrix);
> +		cairo_rectangle(cr, x + width - shadow_width, y + top_margin,
> +				shadow_width, shadow_height);
> +		cairo_reset_clip(cr);
> +		cairo_clip (cr);
> +		cairo_mask(cr, pattern);
> +	}
>  
>  	cairo_pattern_destroy(pattern);
>  	cairo_reset_clip(cr);

Excellent documentation, both in code and commit message. Pushed, both
of them.


Thanks,
pq