Added optional 2d controls that to allow moving and zooming vector images.

vector/glow-extras/vector/backend/opengl.cc

@@ -144,6 +144,19 @@ void ogl_context::render(const image2D& img) const
         void reset_clip() { nvgResetScissor(vg); }
 
         void global_alpha(float a) { nvgGlobalAlpha(vg, a); }
+
+        //        void reset_transform() { nvgResetTransform(vg); }
+        //        void apply_transform(float a, float b, float c, float d, float e, float f) { nvgTransform(vg, a, b, c, d, e, f); }
+        //        void set_transform(float a, float b, float c, float d, float e, float f)
+        //        {
+        //            reset_transform();
+        //            apply_transform(a, b, c, d, e, f);
+        //        }
+        //        void translate(float x, float y) { return nvgTranslate(vg, x, y); }
+        //        void rotate(float angle) { nvgRotate(vg, angle); }
+        //        void skew_x(float angle) { nvgSkewX(vg, angle); }
+        //        void skew_y(float angle) { nvgSkewY(vg, angle); }
+        //        void scale(float x, float y) { nvgScale(vg, x, y); }
     };
 
     visit(img, nvg_renderer{vg});
@@ -199,6 +212,15 @@ ogl_context OGLRenderer::frame(float w, float h, float devicePixelRatio) const
 
     nvgBeginFrame(vg, w, h, devicePixelRatio);
 
+    nvgResetTransform(vg);
+    nvgTransform(vg,                     //
+                 global_transform[0][0], //
+                 global_transform[0][1], //
+                 global_transform[1][0], //
+                 global_transform[1][1], //
+                 global_transform[2][0], //
+                 global_transform[2][1]);
+
     return {vg, bool(was_blending_enabled)};
 }