20 files changed, 388 insertions, 13 deletions

diff --git a/README.md b/README.md
index 5e9016e6..159db607 100644
--- a/README.md
+++ b/README.md
@@ -13,7 +13,11 @@ Sway is an incredible window manager, and certainly one of the most well establi
 
 + Corner radius: `corner_radius <val>`
 + Application saturation: `for_window [CRITERIA HERE] saturation <set|plus|minus> <val 0.0 <-> 2.0>`
-+ Dim unfocused windows: 
++ Window shadows:
+    - `shadows on|off`
+    - `shadow_blur_radius <integer value 0 - 100>`
+    - `shadow_color <hex color with alpha> ex, #0000007F`
++ Dim unfocused windows:
     - `dim_inactive <float value 0.0 - 1.0>`
     - `dim_inactive_colors.unfocused <hex color> ex, #000000FF`
     - `dim_inactive_colors.urgent <hex color> ex, #900000FF`
@@ -22,7 +26,6 @@ Sway is an incredible window manager, and certainly one of the most well establi
 
 + fade in / out animations
 + window movement animations
-+ drop shadows
 + blur
 
 ## Installation
diff --git a/config.in b/config.in
index bcc89de2..174b48f9 100644
--- a/config.in
+++ b/config.in
@@ -24,6 +24,10 @@ set $menu dmenu_path | dmenu | xargs swaymsg exec --
 # window corner radius in px
 corner_radius 10
 
+shadows off
+shadow_blur_radius 20
+shadow_color #0000007F
+
 # inactive window fade amount. 0.0 = no dimming, 1.0 = fully dimmed
 dim_inactive 0.0
 dim_inactive_colors.unfocused #000000FF
diff --git a/include/sway/commands.h b/include/sway/commands.h
index 98b232e1..256b3506 100644
--- a/include/sway/commands.h
+++ b/include/sway/commands.h
@@ -178,6 +178,9 @@ sway_cmd cmd_scratchpad;
 sway_cmd cmd_seamless_mouse;
 sway_cmd cmd_set;
 sway_cmd cmd_shortcuts_inhibitor;
+sway_cmd cmd_shadow_blur_radius;
+sway_cmd cmd_shadow_color;
+sway_cmd cmd_shadows;
 sway_cmd cmd_show_marks;
 sway_cmd cmd_smart_borders;
 sway_cmd cmd_smart_gaps;
diff --git a/include/sway/config.h b/include/sway/config.h
index 55aa8fbe..bcb06f0f 100644
--- a/include/sway/config.h
+++ b/include/sway/config.h
@@ -482,6 +482,9 @@ struct sway_config {
 		float unfocused[4];
 		float urgent[4];
 	} dim_inactive_colors;
+	bool shadow_enabled;
+	int shadow_blur_sigma;
+	float shadow_color[4];
 
 	char *swaynag_command;
 	struct swaynag_instance swaynag_config_errors;
diff --git a/include/sway/desktop/fx_renderer.h b/include/sway/desktop/fx_renderer.h
index c5bae260..1c3121cd 100644
--- a/include/sway/desktop/fx_renderer.h
+++ b/include/sway/desktop/fx_renderer.h
@@ -47,6 +47,8 @@ struct fx_renderer {
 
 	float projection[9];
 
+	GLuint stencil_buffer_id;
+
 	struct {
 		bool OES_egl_image_external;
 	} exts;
@@ -84,6 +86,17 @@ 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 corner_radius;
+		} box_shadow;
+
 		struct gles2_tex_shader tex_rgba;
 		struct gles2_tex_shader tex_rgbx;
 		struct gles2_tex_shader tex_ext;
@@ -118,4 +131,7 @@ 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
diff --git a/include/sway/tree/container.h b/include/sway/tree/container.h
index 75a8113a..91448ac7 100644
--- a/include/sway/tree/container.h
+++ b/include/sway/tree/container.h
@@ -113,6 +113,8 @@ struct sway_container {
 	// Hidden scratchpad containers have a NULL parent.
 	bool scratchpad;
 
+	bool shadow_enabled;
+
 	float saturation;
 
 	float alpha;
diff --git a/sway/commands.c b/sway/commands.c
index 6e473b97..9bd5275d 100644
--- a/sway/commands.c
+++ b/sway/commands.c
@@ -88,6 +88,9 @@ static const struct cmd_handler handlers[] = {
 	{ "popup_during_fullscreen", cmd_popup_during_fullscreen },
 	{ "seat", cmd_seat },
 	{ "set", cmd_set },
+	{ "shadow_blur_radius", cmd_shadow_blur_radius },
+	{ "shadow_color", cmd_shadow_color },
+	{ "shadows", cmd_shadows },
 	{ "show_marks", cmd_show_marks },
 	{ "smart_borders", cmd_smart_borders },
 	{ "smart_gaps", cmd_smart_gaps },
diff --git a/sway/commands/shadow_blur_radius.c b/sway/commands/shadow_blur_radius.c
new file mode 100644
index 00000000..036341f8
--- /dev/null
+++ b/sway/commands/shadow_blur_radius.c
@@ -0,0 +1,25 @@
+#include <string.h>
+#include "sway/commands.h"
+#include "sway/config.h"
+#include "sway/tree/arrange.h"
+#include "sway/tree/container.h"
+#include "log.h"
+
+struct cmd_results *cmd_shadow_blur_radius(int argc, char **argv) {
+	struct cmd_results *error = NULL;
+	if ((error = checkarg(argc, "shadow_blur_radius", EXPECTED_EQUAL_TO, 1))) {
+		return error;
+	}
+
+	char *inv;
+	int value = strtol(argv[0], &inv, 10);
+	if (*inv != '\0' || value < 0 || value > 99) {
+		return cmd_results_new(CMD_FAILURE, "Invalid size specified");
+	}
+
+	config->shadow_blur_sigma = value;
+
+	arrange_root();
+
+	return cmd_results_new(CMD_SUCCESS, NULL);
+}
diff --git a/sway/commands/shadow_color.c b/sway/commands/shadow_color.c
new file mode 100644
index 00000000..02952bdd
--- /dev/null
+++ b/sway/commands/shadow_color.c
@@ -0,0 +1,25 @@
+#include "log.h"
+#include "sway/commands.h"
+#include "sway/config.h"
+#include "sway/output.h"
+#include "sway/tree/arrange.h"
+#include "sway/tree/container.h"
+#include "util.h"
+
+struct cmd_results *cmd_shadow_color(int argc, char **argv) {
+	struct cmd_results *error = NULL;
+	if ((error = checkarg(argc, "shadow_color", EXPECTED_AT_LEAST, 1))) {
+		return error;
+	}
+
+	uint32_t color;
+	if (!parse_color(argv[0], &color)) {
+		return cmd_results_new(CMD_INVALID, "Invalid %s color %s",
+				"shadow_color", argv[0]);
+	}
+	color_to_rgba(config->shadow_color, color);
+
+	arrange_root();
+
+	return cmd_results_new(CMD_SUCCESS, NULL);
+}
diff --git a/sway/commands/shadows.c b/sway/commands/shadows.c
new file mode 100644
index 00000000..2b57b2e6
--- /dev/null
+++ b/sway/commands/shadows.c
@@ -0,0 +1,31 @@
+#include <string.h>
+#include "sway/commands.h"
+#include "sway/config.h"
+#include "sway/tree/arrange.h"
+#include "sway/tree/view.h"
+#include "sway/tree/container.h"
+#include "log.h"
+#include "stringop.h"
+#include "util.h"
+
+struct cmd_results *cmd_shadows(int argc, char **argv) {
+	struct cmd_results *error = checkarg(argc, "shadows", EXPECTED_AT_LEAST, 1);
+
+	if (error) {
+		return error;
+	}
+
+	struct sway_container *con = config->handler_context.container;
+
+	bool result = parse_boolean(argv[0], config->shadow_enabled);
+	if (con == NULL) {
+		config->shadow_enabled = result;
+	} else {
+		con->shadow_enabled = result;
+		container_damage_whole(con);
+	}
+
+	arrange_root();
+
+	return cmd_results_new(CMD_SUCCESS, NULL);
+}
diff --git a/sway/config.c b/sway/config.c
index e99a3458..e965601b 100644
--- a/sway/config.c
+++ b/sway/config.c
@@ -338,6 +338,9 @@ static void config_defaults(struct sway_config *config) {
 	config->dim_inactive = 0.0f;
 	color_to_rgba(config->dim_inactive_colors.unfocused, 0x000000FF);
 	color_to_rgba(config->dim_inactive_colors.urgent, 0x900000FF);
+	config->shadow_enabled = false;
+	config->shadow_blur_sigma = 20.0f;
+	color_to_rgba(config->shadow_color, 0x0000007F);
 
 	// The keysym to keycode translation
 	struct xkb_rule_names rules = {0};
diff --git a/sway/desktop/fx_renderer.c b/sway/desktop/fx_renderer.c
index 782ceb88..03645b0f 100644
--- a/sway/desktop/fx_renderer.c
+++ b/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"
@@ -108,6 +109,7 @@ 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;
 	}
@@ -140,6 +142,7 @@ 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;
 	}
@@ -294,6 +297,20 @@ 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 = glGetAttribLocation(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.corner_radius = glGetUniformLocation(prog, "corner_radius");
+
 	// fragment shaders
 	prog = link_program(common_vert_src, tex_rgba_frag_src);
 	if (!init_frag_shader(&renderer->shaders.tex_rgba, prog)) {
@@ -323,6 +340,7 @@ 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);
@@ -340,6 +358,15 @@ error:
 }
 
 void fx_renderer_begin(struct fx_renderer *renderer, uint32_t width, uint32_t height) {
+	// Create and render the stencil buffer
+	if (renderer->stencil_buffer_id == 0) {
+		glGenRenderbuffers(1, &renderer->stencil_buffer_id);
+	}
+	glBindRenderbuffer(GL_RENDERBUFFER, renderer->stencil_buffer_id);
+	glRenderbufferStorage(GL_RENDERBUFFER, GL_STENCIL_INDEX8, width, height);
+	glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT,
+			GL_RENDERBUFFER, renderer->stencil_buffer_id);
+
 	glViewport(0, 0, width, height);
 
 	// refresh projection matrix
@@ -354,8 +381,9 @@ void fx_renderer_end() {
 }
 
 void fx_renderer_clear(const float color[static 4]) {
-		glClearColor(color[0], color[1], color[2], color[3]);
-		glClear(GL_COLOR_BUFFER_BIT);
+	glClearColor(color[0], color[1], color[2], color[3]);
+	glClearStencil(0);
+	glClear(GL_COLOR_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
 }
 
 void fx_renderer_scissor(struct wlr_box *box) {
@@ -616,3 +644,80 @@ 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 corner_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);
+
+	// Init stencil work
+	// NOTE: Alpha needs to be set to 1.0 to be able to discard any "empty" pixels
+	const float col[4] = {0.0, 0.0, 0.0, 1.0};
+	struct wlr_box inner_box;
+	memcpy(&inner_box, box, sizeof(struct wlr_box));
+	inner_box.x += blur_sigma;
+	inner_box.y += blur_sigma;
+	inner_box.width -= blur_sigma * 2;
+	inner_box.height -= blur_sigma * 2;
+
+	glEnable(GL_STENCIL_TEST);
+	glClearStencil(0);
+	glClear(GL_STENCIL_BUFFER_BIT);
+
+	glStencilFunc(GL_ALWAYS, 1, 0xFF);
+	glStencilOp(GL_KEEP, GL_KEEP, GL_REPLACE);
+	// Disable writing to color buffer
+	glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE);
+	// Draw the rounded rect as a mask
+	fx_render_rounded_rect(renderer, &inner_box, col, projection, corner_radius, ALL);
+	// Close the mask
+	glStencilFunc(GL_NOTEQUAL, 1, 0xFF);
+	glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP);
+	// Reenable writing to color buffer
+	glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
+
+	// 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);
+
+	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
+
+	glUseProgram(renderer->shaders.box_shadow.program);
+
+	glUniformMatrix3fv(renderer->shaders.box_shadow.proj, 1, GL_FALSE, gl_matrix);
+	glUniform4f(renderer->shaders.box_shadow.color, color[0], color[1], color[2], color[3]);
+	glUniform1f(renderer->shaders.box_shadow.blur_sigma, blur_sigma);
+	glUniform1f(renderer->shaders.box_shadow.corner_radius, corner_radius);
+
+	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);
+
+	glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
+
+	glClearStencil(0);
+	glClear(GL_STENCIL_BUFFER_BIT);
+	glDisable(GL_STENCIL_TEST);
+}
diff --git a/sway/desktop/output.c b/sway/desktop/output.c
index 182ca428..abf60a2f 100644
--- a/sway/desktop/output.c
+++ b/sway/desktop/output.c
@@ -746,11 +746,12 @@ static void damage_child_views_iterator(struct sway_container *con,
 void output_damage_whole_container(struct sway_output *output,
 		struct sway_container *con) {
 	// Pad the box by 1px, because the width is a double and might be a fraction
+	int shadow_sigma = con->shadow_enabled ? config->shadow_blur_sigma : 0;
 	struct wlr_box box = {
-		.x = con->current.x - output->lx - 1,
-		.y = con->current.y - output->ly - 1,
-		.width = con->current.width + 2,
-		.height = con->current.height + 2,
+		.x = con->current.x - output->lx - 1 - shadow_sigma,
+		.y = con->current.y - output->ly - 1 - shadow_sigma,
+		.width = con->current.width + 2 + shadow_sigma * 2,
+		.height = con->current.height + 2 + shadow_sigma * 2,
 	};
 	scale_box(&box, output->wlr_output->scale);
 	if (wlr_damage_ring_add_box(&output->damage_ring, &box)) {
diff --git a/sway/desktop/render.c b/sway/desktop/render.c
index 35e2150e..36be155e 100644
--- a/sway/desktop/render.c
+++ b/sway/desktop/render.c
@@ -328,6 +328,47 @@ 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],
+		float blur_sigma, float corner_radius, float border_thickness) {
+	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 + blur_sigma;
+	box.y -= output->ly * wlr_output->scale + blur_sigma;
+	box.width += 2 * blur_sigma;
+	box.height += 2 * blur_sigma;
+
+	// Uses the outer radii of the window for a more realistic look
+	corner_radius = corner_radius + border_thickness;
+
+	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, corner_radius, blur_sigma);
+	}
+
+damage_finish:
+	pixman_region32_fini(&damage);
+}
+
 void premultiply_alpha(float color[4], float opacity) {
 	color[3] *= opacity;
 	color[0] *= color[3];
@@ -431,7 +472,7 @@ static void render_saved_view(struct sway_view *view, struct sway_output *output
 }
 
 /**
- * Render a view's surface and left/bottom/right borders.
+ * Render a view's surface, shadow, and left/bottom/right borders.
  */
 static void render_view(struct sway_output *output, pixman_region32_t *damage,
 		struct sway_container *con, struct border_colors *colors,
@@ -443,7 +484,22 @@ static void render_view(struct sway_output *output, pixman_region32_t *damage,
 		render_view_toplevels(view, output, damage, deco_data);
 	}
 
-	if (con->current.border == B_NONE || con->current.border == B_CSD) {
+	// if CSD borders, don't render borders or shadow
+	if (con->current.border == B_CSD) {
+		return;
+	}
+
+	// render shadow
+	if (con->shadow_enabled && config->shadow_blur_sigma > 0 && config->shadow_color[3] > 0.0) {
+		struct sway_container_state *state = &con->current;
+		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, config->shadow_color,
+			config->shadow_blur_sigma, con->corner_radius,
+			state->border_thickness);
+	}
+
+	if (con->current.border == B_NONE) {
 		return;
 	}
 
diff --git a/sway/desktop/shaders/box_shadow.frag b/sway/desktop/shaders/box_shadow.frag
new file mode 100644
index 00000000..c9b2b91f
--- /dev/null
+++ b/sway/desktop/shaders/box_shadow.frag
@@ -0,0 +1,74 @@
+// Writeup: https://madebyevan.com/shaders/fast-rounded-rectangle-shadows/
+
+precision mediump float;
+varying vec4 v_color;
+varying vec2 v_texcoord;
+
+uniform vec2 position;
+uniform vec2 size;
+uniform float blur_sigma;
+uniform float corner_radius;
+
+float gaussian(float x, float sigma) {
+    const float pi = 3.141592653589793;
+    return exp(-(x * x) / (2.0 * sigma * sigma)) / (sqrt(2.0 * pi) * sigma);
+}
+
+// approximates the error function, needed for the gaussian integral
+vec2 erf(vec2 x) {
+    vec2 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 blurred mask along the x dimension
+float roundedBoxShadowX(float x, float y, float sigma, float corner, vec2 halfSize) {
+    float delta = min(halfSize.y - corner - abs(y), 0.0);
+    float curved = halfSize.x - corner + sqrt(max(0.0, corner * corner - delta * delta));
+    vec2 integral = 0.5 + 0.5 * erf((x + vec2(-curved, curved)) * (sqrt(0.5) / sigma));
+    return integral.y - integral.x;
+}
+
+// return the mask for the shadow of a box from lower to upper
+float roundedBoxShadow(vec2 lower, vec2 upper, vec2 point, float sigma, float corner_radius) {
+    // Center everything to make the math easier
+    vec2 center = (lower + upper) * 0.5;
+    vec2 halfSize = (upper - lower) * 0.5;
+    point -= center;
+
+    // The signal is only non-zero in a limited range, so don't waste samples
+    float low = point.y - halfSize.y;
+    float high = point.y + halfSize.y;
+    float start = clamp(-3.0 * sigma, low, high);
+    float end = clamp(3.0 * sigma, low, high);
+
+    // Accumulate samples (we can get away with surprisingly few samples)
+    float step = (end - start) / 4.0;
+    float y = start + step * 0.5;
+    float value = 0.0;
+    for (int i = 0; i < 4; i++) {
+        value += roundedBoxShadowX(point.x, point.y - y, sigma, corner_radius, halfSize) * gaussian(y, sigma) * step;
+        y += step;
+    }
+
+    return value;
+}
+
+// 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 = v_color.a * roundedBoxShadow(
+            position + blur_sigma,
+            position + size - blur_sigma,
+            gl_FragCoord.xy, blur_sigma * 0.5,
+            corner_radius);
+
+    // dither the alpha to break up color bands
+    frag_alpha += (random() - 0.5) / 128.0;
+
+    gl_FragColor = vec4(v_color.rgb, frag_alpha);
+}
diff --git a/sway/desktop/shaders/meson.build b/sway/desktop/shaders/meson.build
index 08efb967..ce2439de 100644
--- a/sway/desktop/shaders/meson.build
+++ b/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',
diff --git a/sway/desktop/shaders/quad_round.frag b/sway/desktop/shaders/quad_round.frag
index e347284b..ddd6fe9b 100644
--- a/sway/desktop/shaders/quad_round.frag
+++ b/sway/desktop/shaders/quad_round.frag
@@ -7,9 +7,13 @@ uniform vec2 position;
 uniform float radius;
 
 void main() {
-    vec2 half_size = size / 2.0;
+    vec2 half_size = size * 0.5;
     vec2 q = abs(gl_FragCoord.xy - position - half_size) - half_size + radius;
-    float distance = min(max(q.x,q.y),0.0) + length(max(q,0.0)) - radius;
-    float smoothedAlpha = 1.0 - smoothstep(-1.0, 1.0, distance);
+    float dist = min(max(q.x,q.y), 0.0) + length(max(q, 0.0)) - radius;
+    float smoothedAlpha = 1.0 - smoothstep(-1.0, 0.5, dist);
     gl_FragColor = mix(vec4(0), v_color, smoothedAlpha);
+
+    if (gl_FragColor.a == 0.0) {
+        discard;
+    }
 }
diff --git a/sway/meson.build b/sway/meson.build
index 12362fcd..757d0c99 100644
--- a/sway/meson.build
+++ b/sway/meson.build
@@ -106,6 +106,9 @@ sway_sources = files(
 	'commands/seat/shortcuts_inhibitor.c',
 	'commands/seat/xcursor_theme.c',
 	'commands/set.c',
+	'commands/shadow_blur_radius.c',
+	'commands/shadow_color.c',
+	'commands/shadows.c',
 	'commands/show_marks.c',
 	'commands/shortcuts_inhibitor.c',
 	'commands/smart_borders.c',
@@ -250,3 +253,4 @@ executable(
 	link_with: [lib_sway_common],
 	install: true
 )
+
diff --git a/sway/sway.5.scd b/sway/sway.5.scd
index 15e60844..a5fb4173 100644
--- a/sway/sway.5.scd
+++ b/sway/sway.5.scd
@@ -659,6 +659,17 @@ The default colors are:
 *dim_inactive_colors.urgent* <hex color>
 	The color to dim inactive urgent windows with. Example color: #900000FF
 
+*shadows* <value>
+	Adjusts if shadows should be enabled or not (on|off). Can also be set per
+	window with *for_window*.
+
+*shadow_blur_radius* <value>
+	Adjusts the shadow blur radius of windows between 0 (disabled) and 100
+	while 20 is the default value.
+
+*shadow_color* <hex color with alpha>
+	The shadow color. Default color: #0000007F
+
 *default_border* normal|none|pixel [<n>]
 	Set default border style for new tiled windows.
 
diff --git a/sway/tree/container.c b/sway/tree/container.c
index 29a1e226..9de6c551 100644
--- a/sway/tree/container.c
+++ b/sway/tree/container.c
@@ -42,6 +42,7 @@ struct sway_container *container_create(struct sway_view *view) {
 	c->view = view;
 	c->alpha = 1.0f;
 	c->saturation = 1.0f;
+	c->shadow_enabled = config->shadow_enabled;
 	c->corner_radius = config->corner_radius;
 
 	if (!view) {