diff --git a/src/emulator.c b/src/emulator.c
index 044d23d8..b55cfb59 100644
--- a/src/emulator.c
+++ b/src/emulator.c
@@ -85,8 +85,8 @@ static void emu_render_frame(struct emu *emu) {
   /* render the current render context to the video framebuffer */
   framebuffer_handle_t original = r_get_framebuffer(r2);
   r_bind_framebuffer(r2, emu->video_fb);
-  tr_render_context(emu->tr, &emu->video_rc, emu->video_fb_width,
-                    emu->video_fb_height);
+  r_viewport(emu->r, emu->video_fb_width, emu->video_fb_height);
+  tr_render_context(emu->tr, &emu->video_rc);
   r_bind_framebuffer(r2, original);
 
   /* insert fence for main thread to synchronize on in order to ensure that
@@ -148,7 +148,7 @@ static void emu_paint(struct emu *emu) {
 
   nk_update_input(emu->nk);
 
-  r_clear_viewport(emu->r, width, height);
+  r_viewport(emu->r, emu->video_width, emu->video_height);
 
   /* present the latest frame from the video thread */
   {
diff --git a/src/hw/pvr/tr.c b/src/hw/pvr/tr.c
index d4c94c89..3f2cd436 100644
--- a/src/hw/pvr/tr.c
+++ b/src/hw/pvr/tr.c
@@ -930,12 +930,9 @@ static void tr_render_list(struct tr *tr, const struct tr_context *rc,
   }
 }
 
-void tr_render_context(struct tr *tr, const struct tr_context *rc,
-                       int video_width, int video_height) {
+void tr_render_context(struct tr *tr, const struct tr_context *rc) {
   PROF_ENTER("gpu", "tr_render_context");
 
-  r_clear_viewport(tr->r, video_width, video_height);
-
   r_begin_ta_surfaces(tr->r, rc->projection, rc->verts, rc->num_verts);
 
   tr_render_list(tr, rc, TA_LIST_OPAQUE);
diff --git a/src/hw/pvr/tr.h b/src/hw/pvr/tr.h
index 24f6974c..ee0130d3 100644
--- a/src/hw/pvr/tr.h
+++ b/src/hw/pvr/tr.h
@@ -88,7 +88,6 @@ void tr_destroy(struct tr *tr);
 
 void tr_parse_context(struct tr *tr, const struct tile_context *ctx,
                       struct tr_context *rc);
-void tr_render_context(struct tr *tr, const struct tr_context *rc,
-                       int video_width, int video_height);
+void tr_render_context(struct tr *tr, const struct tr_context *rc);
 
 #endif
diff --git a/src/render/gl_backend.c b/src/render/gl_backend.c
index 1b15c01e..5301220d 100644
--- a/src/render/gl_backend.c
+++ b/src/render/gl_backend.c
@@ -66,6 +66,8 @@ struct texture {
 struct render_backend {
   struct host *host;
   gl_context_t ctx;
+  int viewport_width;
+  int viewport_height;
   int debug_flags;
 
   /* default assets created during intitialization */
@@ -563,17 +565,14 @@ void r_begin_ui_surfaces(struct render_backend *r,
                          const struct ui_vertex *verts, int num_verts,
                          const uint16_t *indices, int num_indices) {
   /* setup projection matrix */
-  int width = video_width(r->host);
-  int height = video_height(r->host);
-
   float ortho[16];
-  ortho[0] = 2.0f / (float)width;
+  ortho[0] = 2.0f / (float)r->viewport_width;
   ortho[4] = 0.0f;
   ortho[8] = 0.0f;
   ortho[12] = -1.0f;
 
   ortho[1] = 0.0f;
-  ortho[5] = -2.0f / (float)height;
+  ortho[5] = -2.0f / (float)r->viewport_height;
   ortho[9] = 0.0f;
   ortho[13] = 1.0f;
 
@@ -612,9 +611,20 @@ void r_begin_ui_surfaces(struct render_backend *r,
   }
 }
 
-void r_clear_viewport(struct render_backend *r, int width, int height) {
+int r_viewport_height(struct render_backend *r) {
+  return r->viewport_height;
+}
+
+int r_viewport_width(struct render_backend *r) {
+  return r->viewport_width;
+}
+
+void r_viewport(struct render_backend *r, int width, int height) {
+  r->viewport_width = width;
+  r->viewport_height = height;
+
   glDepthMask(1);
-  glViewport(0, 0, width, height);
+  glViewport(0, 0, r->viewport_width, r->viewport_height);
   glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
   glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 }
@@ -815,14 +825,6 @@ void r_set_debug_flag(struct render_backend *r, int flag) {
   r->debug_flags |= flag;
 }
 
-int r_video_height(struct render_backend *r) {
-  return video_height(r->host);
-}
-
-int r_video_width(struct render_backend *r) {
-  return video_width(r->host);
-}
-
 void r_make_current(struct render_backend *r) {
   video_gl_make_current(r->host, r->ctx);
 }
diff --git a/src/render/microprofile.cc b/src/render/microprofile.cc
index 9fd1c38b..6b68d210 100644
--- a/src/render/microprofile.cc
+++ b/src/render/microprofile.cc
@@ -217,8 +217,8 @@ static void mp_draw_line(struct microprofile *mp, float *verts, int num_verts,
 void mp_render(struct microprofile *mp) {
   s_mp = mp;
 
-  int width = r_video_width(mp->r);
-  int height = r_video_height(mp->r);
+  int width = r_viewport_width(mp->r);
+  int height = r_viewport_height(mp->r);
 
   /* update draw surfaces */
   MicroProfileDraw(width, height);
diff --git a/src/render/nuklear.c b/src/render/nuklear.c
index edfebb58..ea7f3508 100644
--- a/src/render/nuklear.c
+++ b/src/render/nuklear.c
@@ -17,7 +17,7 @@
 #endif
 
 void nk_render(struct nuklear *nk) {
-  float height = (float)r_video_height(nk->r);
+  float height = (float)r_viewport_height(nk->r);
 
   /* convert draw list into vertex / element buffers */
   static const struct nk_draw_vertex_layout_element vertex_layout[] = {
diff --git a/src/render/render_backend.h b/src/render/render_backend.h
index 6e3ccccf..6af8fafc 100644
--- a/src/render/render_backend.h
+++ b/src/render/render_backend.h
@@ -138,9 +138,6 @@ void r_destroy(struct render_backend *rc);
 
 void r_make_current(struct render_backend *r);
 
-int r_video_width(struct render_backend *r);
-int r_video_height(struct render_backend *r);
-
 void r_set_debug_flag(struct render_backend *r, int flag);
 int r_get_debug_flag(struct render_backend *r, int flag);
 void r_clear_debug_flag(struct render_backend *r, int flag);
@@ -165,7 +162,9 @@ sync_handle_t r_insert_sync(struct render_backend *r);
 void r_wait_sync(struct render_backend *r, sync_handle_t handle);
 void r_destroy_sync(struct render_backend *r, sync_handle_t handle);
 
-void r_clear_viewport(struct render_backend *r, int width, int height);
+void r_viewport(struct render_backend *r, int width, int height);
+int r_viewport_width(struct render_backend *r);
+int r_viewport_height(struct render_backend *r);
 
 void r_begin_ta_surfaces(struct render_backend *r, const float *projection,
                          const struct ta_vertex *verts, int num_verts);
diff --git a/src/tracer.c b/src/tracer.c
index e2b4e493..776293dc 100644
--- a/src/tracer.c
+++ b/src/tracer.c
@@ -808,7 +808,7 @@ void tracer_run_frame(struct tracer *tracer) {
   int width = video_width(tracer->host);
   int height = video_height(tracer->host);
 
-  r_clear_viewport(tracer->r, width, height);
+  r_viewport(tracer->r, width, height);
 
   nk_update_input(tracer->nk);