rebase

include/sway/desktop/fx_renderer.h

@@ -84,6 +84,17 @@ struct fx_renderer {
 			GLint half_thickness;
 		} corner;
 
+		struct {
+			GLuint program;
+			GLint proj;
+			GLint color;
+			GLint pos_attrib;
+			GLint position;
+			GLint size;
+			GLint blur_sigma;
+			GLint alpha;
+		} box_shadow;
+
 		struct gles2_tex_shader tex_rgba;
 		struct gles2_tex_shader tex_rgbx;
 		struct gles2_tex_shader tex_ext;
@@ -118,4 +129,7 @@ void fx_render_border_corner(struct fx_renderer *renderer, const struct wlr_box
 		const float color[static 4], const float projection[static 9],
 		enum corner_location corner_location, int radius, int border_thickness);
 
+void fx_render_box_shadow(struct fx_renderer *renderer, const struct wlr_box *box,
+		const float color[static 4], const float projection[static 9], int radius, float blur_sigma);
+
 #endif

sway/desktop/fx_renderer.c

@@ -24,6 +24,7 @@
 #include "quad_round_tl_frag_src.h"
 #include "quad_round_tr_frag_src.h"
 #include "corner_frag_src.h"
+#include "box_shadow_frag_src.h"
 #include "tex_rgba_frag_src.h"
 #include "tex_rgbx_frag_src.h"
 #include "tex_external_frag_src.h"
@@ -43,6 +44,7 @@ static GLuint compile_shader(GLuint type, const GLchar *src) {
 	GLint ok;
 	glGetShaderiv(shader, GL_COMPILE_STATUS, &ok);
 	if (ok == GL_FALSE) {
+		sway_log(SWAY_ERROR, "Failed to compile shader");
 		glDeleteShader(shader);
 		shader = 0;
 	}
@@ -75,6 +77,7 @@ static GLuint link_program(const GLchar *vert_src, const GLchar *frag_src) {
 	GLint ok;
 	glGetProgramiv(prog, GL_LINK_STATUS, &ok);
 	if (ok == GL_FALSE) {
+		sway_log(SWAY_ERROR, "Failed to link shader");
 		glDeleteProgram(prog);
 		goto error;
 	}
@@ -228,6 +231,20 @@ struct fx_renderer *fx_renderer_create(struct wlr_egl *egl) {
 	renderer->shaders.corner.half_size = glGetUniformLocation(prog, "half_size");
 	renderer->shaders.corner.half_thickness = glGetUniformLocation(prog, "half_thickness");
 
+	// box shadow shader
+	prog = link_program(common_vert_src, box_shadow_frag_src);
+	renderer->shaders.box_shadow.program = prog;
+	if (!renderer->shaders.box_shadow.program) {
+		goto error;
+	}
+	renderer->shaders.box_shadow.proj = glGetUniformLocation(prog, "proj");
+	renderer->shaders.box_shadow.color = glGetUniformLocation(prog, "color");
+	renderer->shaders.box_shadow.pos_attrib = glGetUniformLocation(prog, "pos");
+	renderer->shaders.box_shadow.position = glGetUniformLocation(prog, "position");
+	renderer->shaders.box_shadow.size = glGetUniformLocation(prog, "size");
+	renderer->shaders.box_shadow.blur_sigma = glGetUniformLocation(prog, "blur_sigma");
+	renderer->shaders.box_shadow.alpha = glGetUniformLocation(prog, "alpha");
+
 	// fragment shaders
 	prog = link_program(common_vert_src, tex_rgba_frag_src);
 	if (!init_frag_shader(&renderer->shaders.tex_rgba, prog)) {
@@ -253,6 +270,7 @@ error:
 	glDeleteProgram(renderer->shaders.rounded_tl_quad.program);
 	glDeleteProgram(renderer->shaders.rounded_tr_quad.program);
 	glDeleteProgram(renderer->shaders.corner.program);
+	glDeleteProgram(renderer->shaders.box_shadow.program);
 	glDeleteProgram(renderer->shaders.tex_rgba.program);
 	glDeleteProgram(renderer->shaders.tex_rgbx.program);
 	glDeleteProgram(renderer->shaders.tex_ext.program);
@@ -543,3 +561,45 @@ void fx_render_border_corner(struct fx_renderer *renderer, const struct wlr_box
 
 	glDisableVertexAttribArray(renderer->shaders.corner.pos_attrib);
 }
+
+// TODO: alpha input arg
+void fx_render_box_shadow(struct fx_renderer *renderer, const struct wlr_box *box,
+		const float color[static 4], const float projection[static 9], int radius, float blur_sigma) {
+	if (box->width == 0 || box->height == 0) {
+		return;
+	}
+	assert(box->width > 0 && box->height > 0);
+	float matrix[9];
+	wlr_matrix_project_box(matrix, box, WL_OUTPUT_TRANSFORM_NORMAL, 0, projection);
+
+	float gl_matrix[9];
+	wlr_matrix_multiply(gl_matrix, renderer->projection, matrix);
+
+	// TODO: investigate why matrix is flipped prior to this cmd
+	// wlr_matrix_multiply(gl_matrix, flip_180, gl_matrix);
+
+	wlr_matrix_transpose(gl_matrix, gl_matrix);
+
+	// blending will practically always be needed (unless we have a madman
+	// who uses opaque shadows with zero sigma), so just enable it
+	glEnable(GL_BLEND);
+
+	glUseProgram(renderer->shaders.box_shadow.program);
+
+	glUniformMatrix3fv(renderer->shaders.box_shadow.proj, 1, GL_FALSE, gl_matrix);
+	glUniform3f(renderer->shaders.box_shadow.color, color[0], color[1], color[2]);
+	glUniform1f(renderer->shaders.box_shadow.alpha, color[3]);
+	glUniform1f(renderer->shaders.box_shadow.blur_sigma, blur_sigma);
+
+	glUniform2f(renderer->shaders.box_shadow.size, box->width, box->height);
+	glUniform2f(renderer->shaders.box_shadow.position, box->x, box->y);
+
+	glVertexAttribPointer(renderer->shaders.box_shadow.pos_attrib, 2, GL_FLOAT, GL_FALSE,
+			0, verts);
+
+	glEnableVertexAttribArray(renderer->shaders.box_shadow.pos_attrib);
+
+	glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
+
+	glDisableVertexAttribArray(renderer->shaders.box_shadow.pos_attrib);
+}

sway/desktop/render.c

@@ -328,6 +328,39 @@ damage_finish:
 	pixman_region32_fini(&damage);
 }
 
+// _box.x and .y are expected to be layout-local
+// _box.width and .height are expected to be output-buffer-local
+void render_box_shadow(struct sway_output *output, pixman_region32_t *output_damage,
+		const struct wlr_box *_box, const float color[static 4]) {
+	struct wlr_output *wlr_output = output->wlr_output;
+	struct fx_renderer *renderer = output->server->renderer;
+
+	struct wlr_box box;
+	memcpy(&box, _box, sizeof(struct wlr_box));
+	box.x -= output->lx * wlr_output->scale;
+	box.y -= output->ly * wlr_output->scale;
+
+	pixman_region32_t damage;
+	pixman_region32_init(&damage);
+	pixman_region32_union_rect(&damage, &damage, box.x, box.y,
+		box.width, box.height);
+	pixman_region32_intersect(&damage, &damage, output_damage);
+	bool damaged = pixman_region32_not_empty(&damage);
+	if (!damaged) {
+		goto damage_finish;
+	}
+
+	int nrects;
+	pixman_box32_t *rects = pixman_region32_rectangles(&damage, &nrects);
+	for (int i = 0; i < nrects; ++i) {
+		scissor_output(wlr_output, &rects[i]);
+		fx_render_box_shadow(renderer, &box, color, wlr_output->transform_matrix, 0, 0.3);
+	}
+
+damage_finish:
+	pixman_region32_fini(&damage);
+}
+
 void premultiply_alpha(float color[4], float opacity) {
 	color[3] *= opacity;
 	color[0] *= color[3];
@@ -965,6 +998,12 @@ static void render_containers_linear(struct sway_output *output,
 			} else if (state->border == B_PIXEL) {
 				render_top_border(output, damage, state, colors, deco_data.alpha, deco_data.corner_radius);
 			}
+
+			// render shadow
+			const float color[4] = {0,0,0,0.7};
+			struct wlr_box box = {state->x, state->y, state->width, state->height};
+			scale_box(&box, output->wlr_output->scale);
+			render_box_shadow(output, damage, &box, color);
 		} else {
 			render_container(output, damage, child,
 					parent->focused || child->current.focused);

sway/desktop/shaders/box_shadow.frag

@@ -0,0 +1,39 @@
+// Writeup: https://madebyevan.com/shaders/fast-rounded-rectangle-shadows/
+
+precision mediump float;
+varying vec2 v_texcoord;
+
+uniform vec3 color;
+uniform vec2 position;
+uniform vec2 size;
+uniform float blur_sigma;
+uniform float alpha;
+
+// approximates the error function, needed for the gaussian integral
+vec4 erf(vec4 x) {
+    vec4 s = sign(x), a = abs(x);
+    x = 1.0 + (0.278393 + (0.230389 + 0.078108 * (a * a)) * a) * a;
+    x *= x;
+    return s - s / (x * x);
+}
+
+// return the mask for the shadow of a box from lower to upper
+float box_shadow(vec2 lower, vec2 upper, vec2 point, float sigma) {
+    vec4 query = vec4(point - lower, upper - point);
+    vec4 integral = 0.5 + 0.5 * erf(query * (sqrt(0.5) / sigma));
+    return (integral.z - integral.x) * (integral.w - integral.y);
+}
+
+// per-pixel "random" number between 0 and 1
+float random() {
+    return fract(sin(dot(vec2(12.9898, 78.233), gl_FragCoord.xy)) * 43758.5453);
+}
+
+void main() {
+    float frag_alpha = alpha * box_shadow(position, position + size, gl_FragCoord.xy, blur_sigma);
+
+    // dither the alpha to break up color bands
+    frag_alpha += (random() - 0.5) / 128.0;
+
+    gl_FragColor = vec4(color, frag_alpha);
+}

sway/desktop/shaders/meson.build

@@ -7,6 +7,7 @@ shaders = [
     'quad_round_tl.frag',
     'quad_round_tr.frag',
     'corner.frag',
+    'box_shadow.frag',
     'tex_rgba.frag',
     'tex_rgbx.frag',
     'tex_external.frag',