renderer: add scissor test API

src/renderer/api.c

@@ -720,6 +720,19 @@ void r_vertex_array_layout(VertexArray *varr, uint nattribs, VertexAttribFormat
 	B.vertex_array_layout(varr, nattribs, attribs);
 }
 
+void r_scissor(int x, int y, int w, int h) {
+	_r_state_touch_scissor();
+	B.scissor((IntRect) { x, y, w, h });
+}
+
+void r_scissor_rect(IntRect scissor) {
+	B.scissor(scissor);
+}
+
+void r_scissor_current(IntRect *scissor) {
+	B.scissor_current(scissor);
+}
+
 void r_vsync(VsyncMode mode) {
 	B.vsync(mode);
 }

src/renderer/api.h

@@ -793,6 +793,11 @@ void r_vertex_array_attach_index_buffer(VertexArray *varr, IndexBuffer *ibuf) at
 IndexBuffer* r_vertex_array_get_index_attachment(VertexArray *varr)  attr_nonnull(1);
 void r_vertex_array_layout(VertexArray *varr, uint nattribs, VertexAttribFormat attribs[nattribs]) attr_nonnull(1, 3);
 
+// NOTE: setting all parameters to 0 disables the scissor test
+void r_scissor(int x, int y, int w, int h);
+void r_scissor_rect(IntRect scissor);
+void r_scissor_current(IntRect *scissor) attr_nonnull(1);
+
 void r_model_add_static(Model *out_mdl, Primitive prim, size_t num_vertices, GenericModelVertex vertices[num_vertices], size_t num_indices, uint indices[num_indices]);
 const Model *r_model_get_quad(void) attr_returns_nonnull;
 

src/renderer/common/backend.h

@@ -121,6 +121,9 @@ typedef struct RendererFuncs {
 	VertexBuffer* (*vertex_array_get_vertex_attachment)(VertexArray *varr, uint attachment);
 	IndexBuffer* (*vertex_array_get_index_attachment)(VertexArray *varr);
 
+	void (*scissor)(IntRect scissor);
+	void (*scissor_current)(IntRect *scissor);
+
 	void (*vsync)(VsyncMode mode);
 	VsyncMode (*vsync_current)(void);
 

src/renderer/common/state.c

@@ -85,6 +85,10 @@ void r_state_pop(void) {
 		B.framebuffer(S.framebuffer);
 	}
 
+	RESTORE(RSTATE_SCISSOR) {
+		B.scissor(S.scissor);
+	}
+
 	if(_r_state.head == _r_state.stack) {
 		_r_state.head = NULL;
 	} else {
@@ -136,3 +140,9 @@ void _r_state_touch_framebuffer(void) {
 		S.framebuffer = B.framebuffer_current();
 	});
 }
+
+void _r_state_touch_scissor(void) {
+	TAINT(RSTATE_SCISSOR, {
+		B.scissor_current(&S.scissor);
+	});
+}

src/renderer/common/state.h

@@ -20,6 +20,7 @@
 	RSTATE(SHADER) \
 	RSTATE(SHADER_UNIFORMS) \
 	RSTATE(RENDERTARGET) \
+	RSTATE(SCISSOR) \
 
 typedef enum RendererStateID {
 	#define RSTATE(id) RSTATE_ID_##id,
@@ -47,6 +48,7 @@ typedef struct RendererStateRollback {
 	ShaderProgram *shader;
 	// TODO uniforms
 	Framebuffer *framebuffer;
+	IntRect scissor;
 } RendererStateRollback;
 
 void _r_state_touch_capabilities(void);
@@ -57,6 +59,7 @@ void _r_state_touch_depth_func(void);
 void _r_state_touch_shader(void);
 void _r_state_touch_uniform(Uniform *uniform);
 void _r_state_touch_framebuffer(void);
+void _r_state_touch_scissor(void);
 
 void _r_state_init(void);
 void _r_state_shutdown(void);

src/renderer/gl33/framebuffer.c

@@ -181,6 +181,7 @@ void gl33_framebuffer_clear(Framebuffer *framebuffer, ClearBufferFlags flags, co
 	Framebuffer *fb_saved = r_framebuffer_current();
 	r_framebuffer(framebuffer);
 	gl33_sync_framebuffer();
+	gl33_sync_scissor();
 	glClear(glflags);
 	r_framebuffer(fb_saved);
 }

src/renderer/gl33/gl33.c

@@ -106,6 +106,12 @@ static struct {
 		FloatRect default_framebuffer;
 	} viewport;
 
+	struct {
+		IntRect pending;
+		IntRect active;
+		bool active_enabled;
+	} scissor;
+
 	Color color;
 	Color clear_color;
 	float clear_depth;
@@ -379,7 +385,7 @@ static void gl33_apply_capability(RendererCapability cap, bool value) {
 	}
 }
 
-static void transform_viewport_origin(Framebuffer *fb, FloatRect *vp) {
+static int get_framebuffer_height(Framebuffer *fb) {
 	int fb_height = 0;
 
 	if(fb == NULL) {
@@ -396,6 +402,11 @@ static void transform_viewport_origin(Framebuffer *fb, FloatRect *vp) {
 	}
 
 	assert(fb_height > 0);
+	return fb_height;
+}
+
+static void transform_viewport_origin(Framebuffer *fb, FloatRect *vp) {
+	int fb_height = get_framebuffer_height(fb);
 	vp->y = fb_height - vp->y - vp->h;
 }
 
@@ -416,6 +427,37 @@ static void gl33_sync_viewport(void) {
 	}
 }
 
+void gl33_sync_scissor(void) {
+	bool pending_enabled =
+		R.scissor.pending.x &&
+		R.scissor.pending.y &&
+		R.scissor.pending.w &&
+		R.scissor.pending.h;
+
+	if(!pending_enabled) {
+		if(R.scissor.active_enabled) {
+			glDisable(GL_SCISSOR_TEST);
+			R.scissor.active_enabled = false;
+		}
+
+		return;
+	}
+
+	if(!R.scissor.active_enabled) {
+		glEnable(GL_SCISSOR_TEST);
+		R.scissor.active_enabled = true;
+	}
+
+	IntRect scissor = R.scissor.pending;
+	int fb_height = get_framebuffer_height(R.framebuffer.pending);
+	scissor.y = fb_height - scissor.y - scissor.h;
+
+	if(memcmp(&R.scissor.active, &scissor, sizeof(R.scissor.active))) {
+		glScissor(scissor.x, scissor.y, scissor.w, scissor.h);
+		R.scissor.active = scissor;
+	}
+}
+
 static IntExtent gl33_get_default_framebuffer_size(void) {
 	IntExtent s;
 	// TODO: cache this at window creation time and refresh on resize events?
@@ -500,6 +542,7 @@ static void gl33_sync_state(void) {
 	gl33_sync_framebuffer();
 	gl33_sync_shader();
 	gl33_sync_viewport();
+	gl33_sync_scissor();
 	gl33_sync_magic_uniforms();
 	gl33_sync_uniforms(R.progs.active);
 	gl33_sync_texunits(true);
@@ -1380,6 +1423,14 @@ static bool gl33_screenshot(Pixmap *out) {
 	return true;
 }
 
+static void gl33_scissor(IntRect scissor) {
+	R.scissor.pending = scissor;
+}
+
+static void gl33_scissor_current(IntRect *scissor) {
+	*scissor = R.scissor.pending;
+}
+
 RendererBackend _r_backend_gl33 = {
 	.name = "gl33",
 	.funcs = {
@@ -1467,6 +1518,8 @@ RendererBackend _r_backend_gl33 = {
 		.vertex_array_get_vertex_attachment = gl33_vertex_array_get_vertex_attachment,
 		.vertex_array_attach_index_buffer = gl33_vertex_array_attach_index_buffer,
 		.vertex_array_get_index_attachment = gl33_vertex_array_get_index_attachment,
+		.scissor = gl33_scissor,
+		.scissor_current = gl33_scissor_current,
 		.vsync = gl33_vsync,
 		.vsync_current = gl33_vsync_current,
 		.swap = gl33_swap,

src/renderer/gl33/gl33.h

@@ -75,6 +75,7 @@ void gl33_sync_blend_mode(void);
 void gl33_sync_cull_face_mode(void);
 void gl33_sync_depth_test_func(void);
 void gl33_sync_capabilities(void);
+void gl33_sync_scissor(void);
 
 void gl33_buffer_deleted(CommonBuffer *cbuf);
 void gl33_vertex_buffer_deleted(VertexBuffer *vbuf);

src/renderer/null/null.c

@@ -179,6 +179,9 @@ static VertexBuffer* null_vertex_array_get_vertex_attachment(VertexArray *varr,
 static IndexBuffer* null_vertex_array_get_index_attachment(VertexArray *varr) { return (void*)&placeholder; }
 static void null_vertex_array_layout(VertexArray *varr, uint nattribs, VertexAttribFormat attribs[nattribs]) { }
 
+static void null_scissor(IntRect scissor) { }
+static void null_scissor_current(IntRect *scissor) { *scissor = (IntRect) { 0 }; }
+
 static void null_vsync(VsyncMode mode) { }
 static VsyncMode null_vsync_current(void) { return VSYNC_NONE; }
 
@@ -273,6 +276,8 @@ RendererBackend _r_backend_null = {
 		.vertex_array_get_vertex_attachment = null_vertex_array_get_vertex_attachment,
 		.vertex_array_attach_index_buffer = null_vertex_array_attach_index_buffer,
 		.vertex_array_get_index_attachment = null_vertex_array_get_index_attachment,
+		.scissor = null_scissor,
+		.scissor_current = null_scissor_current,
 		.vsync = null_vsync,
 		.vsync_current = null_vsync_current,
 		.swap = null_swap,