feat: add glScissor for dirty rect

include/term.h

@@ -63,6 +63,8 @@ typedef struct {
 		GLuint program;
 		GLuint vao;
 		GLuint vbo;
+		VTermRect scissor;
+		VTermRect damage;
 	} gl_state;
 } term_t;
 

src/term/init.c

@@ -16,8 +16,27 @@ void sig_handler(int sig_type) {
 }
 
 int damage(VTermRect rect, void *user) {
-	// printf("damage: [%d, %d, %d, %d]\n", rect.start_col,
-	//			rect.start_row, rect.end_col, rect.end_row);
+	term_t *state = (term_t *)user;
+	state->gl_state.damage = rect;
+
+	// The idea is to append to the scissor, so that redraw is minimized
+	// If the bounds of damage are past the scissor, increase scissor size
+	if (rect.start_col < state->gl_state.scissor.start_col) {
+		state->gl_state.scissor.start_col = rect.start_col;
+	}
+
+	if (rect.start_row < state->gl_state.scissor.start_row) {
+		state->gl_state.scissor.start_row = rect.start_row;
+	}
+
+	if (rect.end_col > state->gl_state.scissor.end_col) {
+		state->gl_state.scissor.end_col = rect.end_col;
+	}
+
+	if (rect.end_row > state->gl_state.scissor.end_row) {
+		state->gl_state.scissor.end_row = rect.end_row;
+	}
+
 	return 1;
 }
 

src/term/render.c

@@ -4,12 +4,25 @@ void render_term(term_t *state) {
 	glClearColor(0, 0, 0, state->config->opacity);
 	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 
-	// if (state->states.resize) {
-	// 	int draw_width, draw_height;
-	// 	glfwGetFramebufferSize(state->glfw_window, &draw_width, &draw_height);
-	// 	resize_term(state, draw_width, draw_height);
-	// 	state->states.resize = false;
-	// }
+	VTermRect rect = state->gl_state.scissor;
+	int x_advance = state->font.face->size->metrics.max_advance >> 6;
+	int ascent = state->font.face->size->metrics.ascender >> 6;
+	int descent = state->font.face->size->metrics.descender >> 6;
+	int linespace = (ascent - descent);
+
+	int x = rect.start_col * x_advance;
+	int y = state->config->height - (rect.start_row * linespace);
+
+	int width = (rect.end_col) * x_advance;
+	int height = (rect.end_row) * linespace;
+
+	glEnable(GL_SCISSOR_TEST);
+	glScissor(x, y - height, width, height);
+	glDisable(GL_SCISSOR_TEST);
+
+	// This is the 2nd part of the scissor optimization
+	// On each render pass, we reset scissor back to the damage size
+	state->gl_state.scissor = state->gl_state.damage;
 
 	int x_offset = 0;
 
@@ -21,27 +34,21 @@ void render_term(term_t *state) {
 		x_offset = 0;
 	}
 
-	// Render cursor block with pure white bar skulley
-	int font_width = state->font.face->size->metrics.max_advance >> 6;
-	int ascent = state->font.face->size->metrics.ascender >> 6;
-	int descent = state->font.face->size->metrics.descender >> 6;
-	int font_height = ascent - descent;
-
 	glBindBuffer(GL_ARRAY_BUFFER, state->gl_state.vbo);
 	glBindVertexArray(state->gl_state.vao);
 
 	coord_t cursor = {
-		.x = state->cursor.x * font_width,
-		.y = state->cursor.y * font_height,
-		.width = font_width,
-		.height = font_height,
+		.x = state->cursor.x * x_advance,
+		.y = state->cursor.y * linespace,
+		.width = x_advance,
+		.height = linespace,
 	};
 
 	cell_vertex_t cursor_vertices[4] = {
 		{cursor.x, cursor.y, 0.0f, 1.0f},
-		{cursor.x, cursor.y + font_height, 0.0f, 0.0f},
-		{cursor.x + font_width, cursor.y, 1.0f, 1.0f},
-		{cursor.x + font_width, cursor.y + font_height, 1.0f, 0.0f},
+		{cursor.x, cursor.y + linespace, 0.0f, 0.0f},
+		{cursor.x + x_advance, cursor.y, 1.0f, 1.0f},
+		{cursor.x + x_advance, cursor.y + linespace, 1.0f, 0.0f},
 	};
 
 	glBufferData(GL_ARRAY_BUFFER, sizeof(cursor_vertices), cursor_vertices, GL_DYNAMIC_DRAW);

src/term/render/main.c

@@ -3,7 +3,7 @@
 // Called inside of the thread as a bootstrap
 int init_gl_context(term_t *state) {
 	glfwMakeContextCurrent(state->glfw_window);
-	glfwSwapInterval(0);
+	glfwSwapInterval(1);
 
 	log_info("OpenGL Version: %s", glGetString(GL_VERSION));
 	log_info("OpenGL Renderer: %s", glGetString(GL_RENDERER));

src/term/resize.c

@@ -4,6 +4,7 @@ void resize_term(term_t *state, int width, int height) {
 	state->config->width = width;
 	state->config->height = height;
 	update_projection(state);
+	glScissor(0, 0, width, height);
 
 	int ascent = state->font.face->size->metrics.ascender >> 6;
 	int descent = state->font.face->size->metrics.descender >> 6;