From 996b388601605093be968aee52370c906f7297ae Mon Sep 17 00:00:00 2001
From: Tim Sylvester <tim@wetdogweather.com>
Date: Thu, 13 Jul 2023 12:34:14 -0700
Subject: [PATCH] Make stencil mode selection more explicit to fix 3D mode with
 no stenciling (#1369)

---
 src/mbgl/gl/layer_group_gl.cpp | 33 ++++++++++++++++++++++-----------
 1 file changed, 22 insertions(+), 11 deletions(-)

diff --git a/src/mbgl/gl/layer_group_gl.cpp b/src/mbgl/gl/layer_group_gl.cpp
index ea01eebeb..90ccb66b7 100644
--- a/src/mbgl/gl/layer_group_gl.cpp
+++ b/src/mbgl/gl/layer_group_gl.cpp
@@ -51,6 +51,8 @@ void TileLayerGroupGL::render(RenderOrchestrator&, PaintParameters& parameters)
     // `stencilModeFor3D` uses a different stencil mask value each time its called, so if the
     // drawables in this layer use 3D stencil mode, we need to set it up here so that all the
     // drawables end up using the same mode value.
+    // 2D and 3D features in the same layer group is not supported.
+    bool features3d = false;
     bool stencil3d = false;
     gfx::StencilMode stencilMode3d;
 
@@ -63,21 +65,27 @@ void TileLayerGroupGL::render(RenderOrchestrator&, PaintParameters& parameters)
         // Collect the tile IDs relevant to stenciling and update the stencil buffer, if necessary.
         std::set<UnwrappedTileID> tileIDs;
         observeDrawables([&](const gfx::Drawable& drawable) {
-            if (drawable.getEnabled() && drawable.getEnableStencil() && drawable.hasRenderPass(parameters.pass)) {
-                if (drawable.getIs3D()) {
+            if (!drawable.getEnabled() || !drawable.hasRenderPass(parameters.pass)) {
+                return;
+            }
+            if (drawable.getIs3D()) {
+                features3d = true;
+                if (drawable.getEnableStencil()) {
                     stencil3d = true;
                 }
-                if (!stencil3d && drawable.getTileID()) {
-                    tileIDs.emplace(drawable.getTileID()->toUnwrapped());
-                }
+            }
+            if (!features3d && drawable.getEnableStencil() && drawable.getTileID()) {
+                tileIDs.emplace(drawable.getTileID()->toUnwrapped());
             }
         });
 
-        // If we're doing 3D stenciling, set up the single-value stencil mask.
-        // If we're doing 2D stenciling, render each tile with a different value.
-        if (stencil3d) {
-            stencilMode3d = parameters.stencilModeFor3D();
-        } else {
+        // If we're doing 3D stenciling and have any features
+        // to draw, set up the single-value stencil mask.
+        // If we're doing 2D stenciling and have any drawables with tile IDs,
+        // render each tile into the stencil buffer with a different value.
+        if (features3d) {
+            stencilMode3d = stencil3d ? parameters.stencilModeFor3D() : gfx::StencilMode::disabled();
+        } else if (!tileIDs.empty()) {
             parameters.renderTileClippingMasks(tileIDs);
         }
     }
@@ -105,7 +113,10 @@ void TileLayerGroupGL::render(RenderOrchestrator&, PaintParameters& parameters)
             tweaker->execute(drawable, parameters);
         }
 
-        if (stencil3d) {
+        // For layer groups with 3D features, enable either the single-value
+        // stencil mode for features with stencil enabled or disable stenciling.
+        // 2D drawables will set their own stencil mode within `draw`.
+        if (features3d) {
             context.setStencilMode(drawable.getEnableStencil() ? stencilMode3d : gfx::StencilMode::disabled());
         }