expose frustum offset on ios and enable scissor test for metal

Author: yousifd

include/mbgl/mtl/render_pass.hpp

@@ -62,6 +62,7 @@ class RenderPass final : public gfx::RenderPass {
 
     void setCullMode(const MTL::CullMode);
     void setFrontFacingWinding(const MTL::Winding);
+    void setScissorRect(const MTL::ScissorRect);
 
 private:
     void pushDebugGroup(const char* name) override;
@@ -92,6 +93,7 @@ class RenderPass final : public gfx::RenderPass {
 
     MTL::CullMode currentCullMode = MTL::CullModeNone;
     MTL::Winding currentWinding = MTL::WindingClockwise;
+    MTL::ScissorRect currentScissorRect;
 };
 
 } // namespace mtl

platform/ios/src/MLNMapView.h

@@ -508,6 +508,16 @@ MLN_EXPORT
  */
 @property (nonatomic, assign) double tileLodZoomShift;
 
+/**
+ Frustum offset used to disable rendering of elements at the edge of the screen
+
+ Offset applied to camera frustum and scissor rectangle. The camrea frustum is modofied
+ to avoid loading geometry that's behind UI elements at the top of the screen. The scissor
+ rectangle is used to avoid shading fragments that are behind UI elements at the edges of
+ the screen. All values are in logical pixels.
+ */
+@property (nonatomic, assign) UIEdgeInsets frustumOffset;
+
 // MARK: Displaying the User’s Location
 
 /**

platform/ios/src/MLNMapView.mm

@@ -3301,6 +3301,16 @@ -(double)tileLodZoomShift
     return _mbglMap->getTileLodZoomShift();
 }
 
+-(void)setFrustumOffset:(UIEdgeInsets)frustomOffset
+{
+    _mbglMap->setFrustumOffset(MLNEdgeInsetsFromNSEdgeInsets(frustomOffset));
+}
+
+-(UIEdgeInsets)frustumOffset
+{
+    return NSEdgeInsetsFromMLNEdgeInsets(_mbglMap->getFrustumOffset());
+}
+
 // MARK: - Accessibility -
 
 - (NSString *)accessibilityValue

src/mbgl/mtl/drawable.cpp

@@ -121,6 +121,10 @@ MTL::Winding mapWindingMode(const gfx::CullFaceWindingType mode) noexcept {
     }
 }
 
+MTL::ScissorRect getMetalScissorRect(gfx::ScissorRect rect) noexcept {
+    return {static_cast<uint32_t>(rect.x), static_cast<uint32_t>(rect.y), rect.width, rect.height};
+}
+
 } // namespace
 
 void Drawable::setColorMode(const gfx::ColorMode& value) {
@@ -215,6 +219,8 @@ void Drawable::draw(PaintParameters& parameters) const {
     renderPass.setCullMode(cullMode.enabled ? mapCullMode(cullMode.side) : MTL::CullModeNone);
     renderPass.setFrontFacingWinding(mapWindingMode(cullMode.winding));
 
+    renderPass.setScissorRect(getMetalScissorRect(parameters.scissorRect));
+
     if (!impl->pipelineState) {
         impl->pipelineState = shaderMTL.getRenderPipelineState(
             renderable,

src/mbgl/mtl/render_pass.cpp

@@ -78,6 +78,7 @@ void RenderPass::resetState() {
 
     currentCullMode = MTL::CullModeNone;
     currentWinding = MTL::WindingClockwise;
+    currentScissorRect = {0, 0, 0, 0};
 }
 
 namespace {
@@ -216,5 +217,13 @@ void RenderPass::setFrontFacingWinding(const MTL::Winding winding) {
     }
 }
 
+void RenderPass::setScissorRect(const MTL::ScissorRect rect) {
+    if (rect.x != currentScissorRect.x || rect.y != currentScissorRect.y || rect.width != currentScissorRect.width ||
+        rect.height != currentScissorRect.height) {
+        encoder->setScissorRect(rect);
+        currentScissorRect = rect;
+    }
+}
+
 } // namespace mtl
 } // namespace mbgl