Provide user with transformation matrix

example/rotation.c

@@ -16,13 +16,13 @@
 static const GLchar vert_src[] =
 "#version 310 es\n"
 "precision mediump float;\n"
-"layout(location = 0) uniform mat2 transform;\n"
+"layout(location = 0) uniform mat4 transform;\n"
 "layout(location = 0) in vec2 pos;\n"
 "layout(location = 1) in float angle;\n"
 "out float v_angle;\n"
 "void main() {\n"
 "	v_angle = angle;\n"
-"	gl_Position = vec4(transform * pos, 0.0, 1.0);\n"
+"	gl_Position = transform * vec4(pos, 0.0, 1.0);\n"
 "}\n";
 
 static const GLchar frag_src[] =
@@ -38,41 +38,6 @@ static const GLchar frag_src[] =
 "		1.0);\n"
 "}\n";
 
-static const GLfloat transforms[][4] = {
-	[WL_OUTPUT_TRANSFORM_NORMAL] = {
-		1.0f, 0.0f,
-		0.0f, 1.0f,
-	},
-	[WL_OUTPUT_TRANSFORM_90] = {
-		0.0f, -1.0f,
-		1.0f, 0.0f,
-	},
-	[WL_OUTPUT_TRANSFORM_180] = {
-		-1.0f, 0.0f,
-		0.0f, -1.0f,
-	},
-	[WL_OUTPUT_TRANSFORM_270] = {
-		0.0f, 1.0f,
-		-1.0f, 0.0f,
-	},
-	[WL_OUTPUT_TRANSFORM_FLIPPED] = {
-		-1.0f, 0.0f,
-		0.0f, 1.0f,
-	},
-	[WL_OUTPUT_TRANSFORM_FLIPPED_90] = {
-		0.0f, 1.0f,
-		1.0f, 0.0f,
-	},
-	[WL_OUTPUT_TRANSFORM_FLIPPED_180] = {
-		1.0f, 0.0f,
-		0.0f, -1.0f,
-	},
-	[WL_OUTPUT_TRANSFORM_FLIPPED_270] = {
-		0.0f, -1.0f,
-		-1.0f, 0.0f,
-	},
-};
-
 struct state {
 	float angle;
 	struct timespec last_frame;
@@ -172,8 +137,8 @@ static void output_frame(struct wl_listener *listener, void *data) {
 	struct output_state *ostate = wl_container_of(listener, ostate, frame);
 	struct state *s = ostate->state;
 
-	float width = ostate->output->width;
-	float height = ostate->output->height;
+	int32_t width = ostate->output->width;
+	int32_t height = ostate->output->height;
 	glViewport(0, 0, width, height);
 
 	// All of the odd numbered transformations involve a 90 or 270 degree rotation
@@ -183,14 +148,13 @@ static void output_frame(struct wl_listener *listener, void *data) {
 		height = tmp;
 	}
 
-	// Single pixel in gl coordinates
-	float px_w = 2.0f / width;
-	float px_h = 2.0f / height;
+	int32_t mid_w = width / 2;
+	int32_t mid_h = height / 2;
 
 	GLfloat vert_data[] = {
-		-250 * px_w, -250 * px_h, s->angle,
-		   0 * px_w, +250 * px_h, s->angle + 2.0944f, // 120 deg
-		+250 * px_w, -250 * px_h, s->angle + 4.18879f, // 240 deg
+		mid_w - 200, mid_h - 200, s->angle,
+		mid_w, mid_h + 200, s->angle + M_PI * 2.0f / 3.0f, // 120 deg
+		mid_w + 200, mid_h - 200, s->angle + M_PI * 4.0f / 3.0f, // 240 deg
 	};
 
 	glUseProgram(s->gl.prog);
@@ -199,7 +163,7 @@ static void output_frame(struct wl_listener *listener, void *data) {
 	glBindBuffer(GL_ARRAY_BUFFER, s->gl.vbo);
 	glBufferData(GL_ARRAY_BUFFER, sizeof(vert_data), vert_data, GL_STATIC_DRAW);
 
-	glUniformMatrix2fv(0, 1, GL_FALSE, transforms[ostate->output->transform]);
+	glUniformMatrix4fv(0, 1, GL_TRUE, ostate->output->transform_matrix);
 
 	glClearColor(0.0, 0.0, 0.0, 1.0);
 	glClear(GL_COLOR_BUFFER_BIT);

include/wlr/types.h

@@ -32,6 +32,8 @@ struct wlr_output {
 	int32_t subpixel; // enum wl_output_subpixel
 	int32_t transform; // enum wl_output_transform
 
+	float transform_matrix[16];
+
 	list_t *modes;
 	struct wlr_output_mode *current_mode;
 

types/wlr_output.c

@@ -1,9 +1,70 @@
 #include <stdlib.h>
+#include <string.h>
+#include <tgmath.h>
 #include <wayland-server.h>
 #include <wlr/types.h>
 #include <wlr/common/list.h>
 #include "types.h"
 
+static const float transforms[][4] = {
+	[WL_OUTPUT_TRANSFORM_NORMAL] = {
+		1.0f, 0.0f,
+		0.0f, 1.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_90] = {
+		0.0f, -1.0f,
+		1.0f, 0.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_180] = {
+		-1.0f, 0.0f,
+		0.0f, -1.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_270] = {
+		0.0f, 1.0f,
+		-1.0f, 0.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_FLIPPED] = {
+		-1.0f, 0.0f,
+		0.0f, 1.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_FLIPPED_90] = {
+		0.0f, 1.0f,
+		1.0f, 0.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_FLIPPED_180] = {
+		1.0f, 0.0f,
+		0.0f, -1.0f,
+	},
+	[WL_OUTPUT_TRANSFORM_FLIPPED_270] = {
+		0.0f, -1.0f,
+		-1.0f, 0.0f,
+	},
+};
+
+// Equivilent to glOrtho(0, width, 0, height, 1, -1) with the transform applied
+static void set_matrix(float mat[static 16], int32_t width, int32_t height,
+		enum wl_output_transform transform) {
+	memset(mat, 0, sizeof(*mat) * 16);
+
+	const float *t = transforms[transform];
+	float x = 2.0f / width;
+	float y = 2.0f / height;
+
+	// Rotation + relection
+	mat[0] = x * t[0];
+	mat[1] = x * t[1];
+	mat[4] = y * t[2];
+	mat[5] = y * t[3];
+
+	// Translation
+	mat[3] = -copysign(1.0f, mat[0] + mat[1]);
+	mat[7] = -copysign(1.0f, mat[4] + mat[5]);
+
+	// Identity
+	mat[10] = 1.0f;
+	mat[15] = 1.0f;
+}
+
 struct wlr_output *wlr_output_create(struct wlr_output_impl *impl,
 		struct wlr_output_state *state) {
 	struct wlr_output *output = calloc(1, sizeof(struct wlr_output));
@@ -20,19 +81,21 @@ void wlr_output_enable(struct wlr_output *output, bool enable) {
 }
 
 bool wlr_output_set_mode(struct wlr_output *output, struct wlr_output_mode *mode) {
+	set_matrix(output->transform_matrix, mode->width, mode->height, output->transform);
 	return output->impl->set_mode(output->state, mode);
 }
 
 void wlr_output_transform(struct wlr_output *output,
 		enum wl_output_transform transform) {
+	set_matrix(output->transform_matrix, output->width, output->height, transform);
 	output->impl->transform(output->state, transform);
 }
 
 void wlr_output_destroy(struct wlr_output *output) {
 	if (!output) return;
 	output->impl->destroy(output->state);
-	if (output->make) free(output->make);
-	if (output->model) free(output->model);
+	free(output->make);
+	free(output->model);
 	for (size_t i = 0; output->modes && i < output->modes->length; ++i) {
 		free(output->modes->items[i]);
 	}