vtgl

Commit: 5598a7bf48dc0f834bf5f792d3767a1bff47e57e
Parent: f7448063875eb0c1cbbaa86e7c02b4754f59128c
Author: Randy Palamar
Date:   Sun,  8 Dec 2024 20:56:48 -0700

use a spin lock in render thread to prevent a missed redraw

Diffstat:
M
vtgl.c
 | 
39
++++++++++++++++++++-------------------

1 file changed, 20 insertions(+), 19 deletions(-)
diff --git a/vtgl.c b/vtgl.c
@@ -1259,24 +1259,24 @@ DEBUG_EXPORT VTGL_RENDER_FRAME_FN(vtgl_render_frame)
 	glBindFramebuffer(GL_FRAMEBUFFER, t->gl.fb);
 	clear_colour();
 
-	b32 can_render_term = atomic_exchange_n(&t->resize_lock, 1) == 0;
-	if (can_render_term) {
-		if (t->gl.flags & RESIZE_RENDERER)
-			resize(t, &memory->platform_api, input->window_size);
-
-		if (t->gl.queued_render) {
-			t->gl.queued_render = 0;
-			u32 cell_count = t->size.h * t->size.w;
-			RenderCell *render_buf = alloc(&arena, RenderCell, cell_count);
-			render_framebuffer(t, render_buf, input, arena);
-			glBufferSubData(GL_SHADER_STORAGE_BUFFER, 0,
-			                cell_count * sizeof(*render_buf), render_buf);
-		}
-		render_cursor(t, input->window_focused, arena);
-		t->resize_lock = 0;
-	} else if (t->gl.queued_render) {
-		input->pending_updates = 1;
+	/* NOTE(rnp): spin lock here so that we don't have to deal with rescheduling
+	 * a redraw. Remember that this failing is already unlikely. */
+	while (atomic_exchange_n(&t->resize_lock, 1) != 0);
+
+	if (t->gl.flags & RESIZE_RENDERER)
+		resize(t, &memory->platform_api, input->window_size);
+
+	if (t->gl.queued_render) {
+		t->gl.queued_render = 0;
+		u32 cell_count = t->size.h * t->size.w;
+		RenderCell *render_buf = alloc(&arena, RenderCell, cell_count);
+		render_framebuffer(t, render_buf, input, arena);
+		glBufferSubData(GL_SHADER_STORAGE_BUFFER, 0,
+		                cell_count * sizeof(*render_buf), render_buf);
 	}
+	render_cursor(t, input->window_focused, arena);
+
+	t->resize_lock = 0;
 
 	ShaderParameters *sp = &t->gl.shader_parameters;
 	sp->blink_parameter += 2 * PI * g_blink_speed * dt_for_frame;
@@ -1333,8 +1333,9 @@ DEBUG_EXPORT VTGL_FRAME_STEP_FN(vtgl_frame_step)
 	t->temp_arena = begin_temp_arena(&t->arena_for_frame);
 
 	if (t->gl.flags & NEEDS_RESIZE || !equal_iv2(input->window_size, t->gl.window_size)) {
-		b32 can_resize_term = atomic_exchange_n(&t->resize_lock, 1) == 0;
-		if (can_resize_term) {
+		/* NOTE(rnp): we skip the resize this time through so that we don't add
+		 * input latency waiting for the render thread to release this lock */
+		if (atomic_exchange_n(&t->resize_lock, 1) == 0) {
 			resize_terminal(t, &memory->platform_api, input->window_size);
 			t->resize_lock = 0;
 		} else {