add scale_filter output config option

include/sway/commands.h

@@ -276,6 +276,7 @@ sway_cmd output_cmd_max_render_time;
 sway_cmd output_cmd_mode;
 sway_cmd output_cmd_position;
 sway_cmd output_cmd_scale;
+sway_cmd output_cmd_scale_filter;
 sway_cmd output_cmd_subpixel;
 sway_cmd output_cmd_toggle;
 sway_cmd output_cmd_transform;

include/sway/config.h

@@ -204,6 +204,13 @@ enum config_dpms {
 	DPMS_OFF
 };
 
+enum scale_filter_mode {
+	SCALE_FILTER_DEFAULT, // the default is currently smart
+	SCALE_FILTER_LINEAR,
+	SCALE_FILTER_NEAREST,
+	SCALE_FILTER_SMART
+};
+
 /**
  * Size and position configuration for a particular output.
  *
@@ -217,6 +224,7 @@ struct output_config {
 	int custom_mode;
 	int x, y;
 	float scale;
+	enum scale_filter_mode scale_filter;
 	int32_t transform;
 	enum wl_output_subpixel subpixel;
 	int max_render_time; // In milliseconds
@@ -655,6 +663,8 @@ int output_name_cmp(const void *item, const void *data);
 void output_get_identifier(char *identifier, size_t len,
 	struct sway_output *output);
 
+const char *sway_output_scale_filter_to_string(enum scale_filter_mode scale_filter);
+
 struct output_config *new_output_config(const char *name);
 
 void merge_output_config(struct output_config *dst, struct output_config *src);

include/sway/output.h

@@ -32,6 +32,7 @@ struct sway_output {
 	int lx, ly; // layout coords
 	int width, height; // transformed buffer size
 	enum wl_output_subpixel detected_subpixel;
+	enum scale_filter_mode scale_filter;
 	// last applied mode when the output is DPMS'ed
 	struct wlr_output_mode *current_mode;
 

meson.build

@@ -48,6 +48,7 @@ pango          = dependency('pango')
 pangocairo     = dependency('pangocairo')
 gdk_pixbuf     = dependency('gdk-pixbuf-2.0', required: get_option('gdk-pixbuf'))
 pixman         = dependency('pixman-1')
+glesv2         = dependency('glesv2')
 libevdev       = dependency('libevdev')
 libinput       = dependency('libinput', version: '>=1.6.0')
 systemd        = dependency('libsystemd', version: '>=239', required: false)

sway/commands/output.c

@@ -19,6 +19,7 @@ static struct cmd_handler output_handlers[] = {
 	{ "res", output_cmd_mode },
 	{ "resolution", output_cmd_mode },
 	{ "scale", output_cmd_scale },
+	{ "scale_filter", output_cmd_scale_filter },
 	{ "subpixel", output_cmd_subpixel },
 	{ "toggle", output_cmd_toggle },
 	{ "transform", output_cmd_transform },

sway/commands/output/scale_filter.c

@@ -0,0 +1,34 @@
+#include <string.h>
+#include "log.h"
+#include "sway/commands.h"
+#include "sway/config.h"
+#include "sway/output.h"
+
+struct cmd_results *output_cmd_scale_filter(int argc, char **argv) {
+	if (!config->handler_context.output_config) {
+		return cmd_results_new(CMD_FAILURE, "Missing output config");
+	}
+
+	if (!argc) {
+		return cmd_results_new(CMD_INVALID, "Missing scale_filter argument.");
+	}
+
+
+	enum scale_filter_mode scale_filter;
+	if (strcmp(*argv, "linear") == 0) {
+		scale_filter = SCALE_FILTER_LINEAR;
+	} else if (strcmp(*argv, "nearest") == 0) {
+		scale_filter = SCALE_FILTER_NEAREST;
+	} else if (strcmp(*argv, "smart") == 0) {
+		scale_filter = SCALE_FILTER_SMART;
+	} else {
+		return cmd_results_new(CMD_INVALID, "Invalid output scale_filter.");
+	}
+
+	struct output_config *oc = config->handler_context.output_config;
+	config->handler_context.leftovers.argc = argc - 1;
+	config->handler_context.leftovers.argv = argv + 1;
+
+	oc->scale_filter = scale_filter;
+	return NULL;
+}

sway/config/output.c

@@ -29,6 +29,21 @@ void output_get_identifier(char *identifier, size_t len,
 		wlr_output->serial);
 }
 
+const char *sway_output_scale_filter_to_string(enum scale_filter_mode scale_filter) {
+	switch (scale_filter) {
+	case SCALE_FILTER_DEFAULT:
+		return "smart";
+	case SCALE_FILTER_LINEAR:
+		return "linear";
+	case SCALE_FILTER_NEAREST:
+		return "nearest";
+	case SCALE_FILTER_SMART:
+		return "smart";
+	}
+	sway_assert(false, "Unknown value for scale_filter.");
+	return NULL;
+}
+
 struct output_config *new_output_config(const char *name) {
 	struct output_config *oc = calloc(1, sizeof(struct output_config));
 	if (oc == NULL) {
@@ -45,6 +60,7 @@ struct output_config *new_output_config(const char *name) {
 	oc->custom_mode = -1;
 	oc->x = oc->y = -1;
 	oc->scale = -1;
+	oc->scale_filter = SCALE_FILTER_DEFAULT;
 	oc->transform = -1;
 	oc->subpixel = WL_OUTPUT_SUBPIXEL_UNKNOWN;
 	oc->max_render_time = -1;
@@ -70,6 +86,9 @@ void merge_output_config(struct output_config *dst, struct output_config *src) {
 	if (src->scale != -1) {
 		dst->scale = src->scale;
 	}
+	if (src->scale_filter != SCALE_FILTER_DEFAULT) {
+		dst->scale_filter = src->scale_filter;
+	}
 	if (src->subpixel != WL_OUTPUT_SUBPIXEL_UNKNOWN) {
 		dst->subpixel = src->subpixel;
 	}
@@ -297,6 +316,24 @@ bool apply_output_config(struct output_config *oc, struct sway_output *output) {
 	if (oc && oc->scale > 0) {
 		sway_log(SWAY_DEBUG, "Set %s scale to %f", oc->name, oc->scale);
 		wlr_output_set_scale(wlr_output, oc->scale);
+
+		enum scale_filter_mode scale_filter_old = output->scale_filter;
+		switch (oc->scale_filter) {
+			case SCALE_FILTER_DEFAULT:
+			case SCALE_FILTER_SMART:
+				output->scale_filter = ceilf(wlr_output->scale) == wlr_output->scale ?
+					SCALE_FILTER_NEAREST : SCALE_FILTER_LINEAR;
+				break;
+			case SCALE_FILTER_LINEAR:
+			case SCALE_FILTER_NEAREST:
+				output->scale_filter = oc->scale_filter;
+				break;
+		}
+		if (scale_filter_old != output->scale_filter) {
+			sway_log(SWAY_DEBUG, "Set %s scale_filter to %s", oc->name,
+				sway_output_scale_filter_to_string(output->scale_filter));
+			output_damage_whole(output);
+		}
 	}
 
 	if (oc && (oc->subpixel != WL_OUTPUT_SUBPIXEL_UNKNOWN || config->reloading)) {
@@ -352,6 +389,7 @@ static void default_output_config(struct output_config *oc,
 	}
 	oc->x = oc->y = -1;
 	oc->scale = 1;
+	oc->scale_filter = SCALE_FILTER_DEFAULT;
 	struct sway_output *output = wlr_output->data;
 	oc->subpixel = output->detected_subpixel;
 	oc->transform = WL_OUTPUT_TRANSFORM_NORMAL;

sway/desktop/render.c

@@ -1,9 +1,11 @@
 #define _POSIX_C_SOURCE 200809L
 #include <assert.h>
+#include <GLES2/gl2.h>
 #include <stdlib.h>
 #include <strings.h>
 #include <time.h>
 #include <wayland-server-core.h>
+#include <wlr/render/gles2.h>
 #include <wlr/render/wlr_renderer.h>
 #include <wlr/types/wlr_box.h>
 #include <wlr/types/wlr_buffer.h>
@@ -70,6 +72,28 @@ static void scissor_output(struct wlr_output *wlr_output,
 	wlr_renderer_scissor(renderer, &box);
 }
 
+static void set_scale_filter(struct wlr_output *wlr_output,
+		struct wlr_texture *texture, enum scale_filter_mode scale_filter) {
+	if (!wlr_texture_is_gles2(texture)) {
+		return;
+	}
+
+	struct wlr_gles2_texture_attribs attribs;
+	wlr_gles2_texture_get_attribs(texture, &attribs);
+
+	switch (scale_filter) {
+	case SCALE_FILTER_LINEAR:
+		glTexParameteri(attribs.target, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
+		break;
+	case SCALE_FILTER_NEAREST:
+		glTexParameteri(attribs.target, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+		break;
+	case SCALE_FILTER_DEFAULT:
+	case SCALE_FILTER_SMART:
+		assert(false); // unreachable
+	}
+}
+
 static void render_texture(struct wlr_output *wlr_output,
 		pixman_region32_t *output_damage, struct wlr_texture *texture,
 		const struct wlr_box *box, const float matrix[static 9], float alpha) {
@@ -119,6 +143,7 @@ static void render_surface_iterator(struct sway_output *output, struct sway_view
 	wlr_matrix_project_box(matrix, &box, transform, rotation,
 		wlr_output->transform_matrix);
 
+	set_scale_filter(wlr_output, texture, output->scale_filter);
 	render_texture(wlr_output, output_damage, texture, &box, matrix, alpha);
 
 	wlr_presentation_surface_sampled_on_output(server.presentation, surface,
@@ -268,6 +293,7 @@ static void render_saved_view(struct sway_view *view,
 	wlr_matrix_project_box(matrix, &box, WL_OUTPUT_TRANSFORM_NORMAL, 0,
 		wlr_output->transform_matrix);
 
+	set_scale_filter(wlr_output, view->saved_buffer->texture, output->scale_filter);
 	render_texture(wlr_output, damage, view->saved_buffer->texture,
 			&box, matrix, alpha);
 

sway/ipc-json.c

@@ -177,6 +177,9 @@ static void ipc_json_describe_output(struct sway_output *output,
 			json_object_new_string(wlr_output->serial));
 	json_object_object_add(object, "scale",
 			json_object_new_double(wlr_output->scale));
+	json_object_object_add(object, "scale_filter",
+		json_object_new_string(
+			sway_output_scale_filter_to_string(output->scale_filter)));
 	json_object_object_add(object, "transform",
 		json_object_new_string(
 			ipc_json_output_transform_description(wlr_output->transform)));

sway/meson.build

@@ -182,6 +182,7 @@ sway_sources = files(
 	'commands/output/mode.c',
 	'commands/output/position.c',
 	'commands/output/scale.c',
+	'commands/output/scale_filter.c',
 	'commands/output/subpixel.c',
 	'commands/output/toggle.c',
 	'commands/output/transform.c',
@@ -203,6 +204,7 @@ sway_deps = [
 	math,
 	pango,
 	pcre,
+	glesv2,
 	pixman,
 	server_protos,
 	wayland_server,

sway/sway-output.5.scd

@@ -70,6 +70,14 @@ must be separated by one space. For example:
 	applications to taste. HiDPI isn't supported with Xwayland clients (windows
 	will blur).
 
+*output* <name> scale_filter linear|nearest|smart
+	Indicates how to scale application buffers that are rendered at a scale
+	lower than the output's configured scale, such as lo-dpi applications on
+	hi-dpi screens. Linear is smoother and blurrier, nearest (also known as
+	nearest neighbor) is sharper and blockier. Setting "smart" will apply
+	nearest scaling when the output has an integer scale factor, otherwise
+	linear. The default is "smart".
+
 *output* <name> subpixel rgb|bgr|vrgb|vbgr|none
 	Manually sets the subpixel hinting for the specified output. This value is
 	usually auto-detected, but some displays may misreport their subpixel

sway/tree/output.c

@@ -93,6 +93,7 @@ struct sway_output *output_create(struct wlr_output *wlr_output) {
 	output->wlr_output = wlr_output;
 	wlr_output->data = output;
 	output->detected_subpixel = wlr_output->subpixel;
+	output->scale_filter = SCALE_FILTER_NEAREST;
 
 	wl_signal_init(&output->events.destroy);
 

swaymsg/main.c

@@ -189,11 +189,13 @@ static void pretty_print_output(json_object *o) {
 	json_object_object_get_ex(o, "focused", &focused);
 	json_object_object_get_ex(o, "active", &active);
 	json_object_object_get_ex(o, "current_workspace", &ws);
-	json_object *make, *model, *serial, *scale, *subpixel, *transform, *max_render_time;
+	json_object *make, *model, *serial, *scale, *scale_filter, *subpixel,
+		*transform, *max_render_time;
 	json_object_object_get_ex(o, "make", &make);
 	json_object_object_get_ex(o, "model", &model);
 	json_object_object_get_ex(o, "serial", &serial);
 	json_object_object_get_ex(o, "scale", &scale);
+	json_object_object_get_ex(o, "scale_filter", &scale_filter);
 	json_object_object_get_ex(o, "subpixel_hinting", &subpixel);
 	json_object_object_get_ex(o, "transform", &transform);
 	json_object_object_get_ex(o, "max_render_time", &max_render_time);
@@ -214,6 +216,7 @@ static void pretty_print_output(json_object *o) {
 			"  Current mode: %dx%d @ %f Hz\n"
 			"  Position: %d,%d\n"
 			"  Scale factor: %f\n"
+			"  Scale filter: %s\n"
 			"  Subpixel hinting: %s\n"
 			"  Transform: %s\n"
 			"  Workspace: %s\n"
@@ -228,6 +231,7 @@ static void pretty_print_output(json_object *o) {
 			(float)json_object_get_int(refresh) / 1000,
 			json_object_get_int(x), json_object_get_int(y),
 			json_object_get_double(scale),
+			json_object_get_string(scale_filter),
 			json_object_get_string(subpixel),
 			json_object_get_string(transform),
 			json_object_get_string(ws)