HiSilicon fix: software clipping for line layer

src/render/draw_line.ts

@@ -119,7 +119,7 @@ export function drawLine(painter: Painter, sourceCache: SourceCache, layer: Line
         }
 
         program.draw(context, gl.TRIANGLES, depthMode,
-            painter.stencilModeForClipping(coord), colorMode, CullFaceMode.backCCW, uniformValues, terrainData, projectionData,
+            painter.stencilModeForClipping(coord), colorMode, CullFaceMode.disabled, uniformValues, terrainData, projectionData,
             layer.id, bucket.layoutVertexBuffer, bucket.indexBuffer, bucket.segments,
             layer.paint, painter.transform.zoom, programConfiguration, bucket.layoutVertexBuffer2);
 

src/shaders/line.fragment.glsl

@@ -3,6 +3,9 @@ uniform lowp float u_device_pixel_ratio;
 in vec2 v_width2;
 in vec2 v_normal;
 in float v_gamma_scale;
+#ifdef GLOBE
+in float v_depth;
+#endif
 
 #pragma mapbox: define highp vec4 color
 #pragma mapbox: define lowp float blur
@@ -24,6 +27,17 @@ void main() {
 
     fragColor = color * (alpha * opacity);
 
+    #ifdef GLOBE
+    if (v_depth > 1.0) {
+        // Hides lines that are visible on the backfacing side of the globe.
+        // This is needed, because some hardware seems to apply glDepthRange first and then apply clipping, which is the wrong order.
+        // Other layers fix this by using backface culling, but the line layer's geometry (actually drawn as polygons) is complex and partly resolved in the shader,
+        // so we can't easily ensure that all triangles have the proper winding order in the vertex buffer creation step.
+        // Thus we render line geometry without face culling, and clip the lines manually here.
+        discard;
+    }
+    #endif
+
 #ifdef OVERDRAW_INSPECTOR
     fragColor = vec4(1.0);
 #endif

src/shaders/line.vertex.glsl

@@ -18,6 +18,9 @@ out vec2 v_normal;
 out vec2 v_width2;
 out float v_gamma_scale;
 out highp float v_linesofar;
+#ifdef GLOBE
+out float v_depth;
+#endif
 
 #pragma mapbox: define highp vec4 color
 #pragma mapbox: define lowp float blur
@@ -77,6 +80,9 @@ void main() {
     vec4 projected_no_extrude = projectTile(pos + offset2 / u_ratio * adjustedThickness + u_translation);
     vec4 projected_with_extrude = projectTile(pos + offset2 / u_ratio * adjustedThickness + u_translation + dist / u_ratio * adjustedThickness);
     gl_Position = projected_with_extrude;
+    #ifdef GLOBE
+    v_depth = gl_Position.z / gl_Position.w;
+    #endif
 
     // calculate how much the perspective view squishes or stretches the extrude
     #ifdef TERRAIN3D

src/shaders/line_gradient.fragment.glsl

@@ -5,6 +5,9 @@ in vec2 v_width2;
 in vec2 v_normal;
 in float v_gamma_scale;
 in highp vec2 v_uv;
+#ifdef GLOBE
+in float v_depth;
+#endif
 
 #pragma mapbox: define lowp float blur
 #pragma mapbox: define lowp float opacity
@@ -28,6 +31,13 @@ void main() {
 
     fragColor = color * (alpha * opacity);
 
+    #ifdef GLOBE
+    if (v_depth > 1.0) {
+        // See comment in line.fragment.glsl
+        discard;
+    }
+    #endif
+
 #ifdef OVERDRAW_INSPECTOR
     fragColor = vec4(1.0);
 #endif

src/shaders/line_gradient.vertex.glsl

@@ -21,6 +21,9 @@ out vec2 v_normal;
 out vec2 v_width2;
 out float v_gamma_scale;
 out highp vec2 v_uv;
+#ifdef GLOBE
+out float v_depth;
+#endif
 
 #pragma mapbox: define lowp float blur
 #pragma mapbox: define lowp float opacity
@@ -80,6 +83,9 @@ void main() {
     vec4 projected_no_extrude = projectTile(pos + offset2 / u_ratio * adjustedThickness + u_translation);
     vec4 projected_with_extrude = projectTile(pos + offset2 / u_ratio * adjustedThickness + u_translation + dist / u_ratio * adjustedThickness);
     gl_Position = projected_with_extrude;
+    #ifdef GLOBE
+    v_depth = gl_Position.z / gl_Position.w;
+    #endif
 
     // calculate how much the perspective view squishes or stretches the extrude
     #ifdef TERRAIN3D

src/shaders/line_pattern.fragment.glsl

@@ -13,6 +13,9 @@ in vec2 v_width2;
 in float v_linesofar;
 in float v_gamma_scale;
 in float v_width;
+#ifdef GLOBE
+in float v_depth;
+#endif
 
 #pragma mapbox: define lowp vec4 pattern_from
 #pragma mapbox: define lowp vec4 pattern_to
@@ -71,6 +74,13 @@ void main() {
 
     fragColor = color * alpha * opacity;
 
+    #ifdef GLOBE
+    if (v_depth > 1.0) {
+        // See comment in line.fragment.glsl
+        discard;
+    }
+    #endif
+
 #ifdef OVERDRAW_INSPECTOR
     fragColor = vec4(1.0);
 #endif

src/shaders/line_pattern.vertex.glsl

@@ -23,6 +23,9 @@ out vec2 v_width2;
 out float v_linesofar;
 out float v_gamma_scale;
 out float v_width;
+#ifdef GLOBE
+out float v_depth;
+#endif
 
 #pragma mapbox: define lowp float blur
 #pragma mapbox: define lowp float opacity
@@ -89,6 +92,9 @@ void main() {
     vec4 projected_no_extrude = projectTile(pos + offset2 / u_ratio * adjustedThickness + u_translation);
     vec4 projected_with_extrude = projectTile(pos + offset2 / u_ratio * adjustedThickness + u_translation + dist / u_ratio * adjustedThickness);
     gl_Position = projected_with_extrude;
+    #ifdef GLOBE
+    v_depth = gl_Position.z / gl_Position.w;
+    #endif
 
     // calculate how much the perspective view squishes or stretches the extrude
     #ifdef TERRAIN3D

src/shaders/line_sdf.fragment.glsl

@@ -9,6 +9,9 @@ in vec2 v_width2;
 in vec2 v_tex_a;
 in vec2 v_tex_b;
 in float v_gamma_scale;
+#ifdef GLOBE
+in float v_depth;
+#endif
 
 #pragma mapbox: define highp vec4 color
 #pragma mapbox: define lowp float blur
@@ -39,6 +42,13 @@ void main() {
 
     fragColor = color * (alpha * opacity);
 
+    #ifdef GLOBE
+    if (v_depth > 1.0) {
+        // See comment in line.fragment.glsl
+        discard;
+    }
+    #endif
+
 #ifdef OVERDRAW_INSPECTOR
     fragColor = vec4(1.0);
 #endif

src/shaders/line_sdf.vertex.glsl

@@ -27,6 +27,9 @@ out vec2 v_width2;
 out vec2 v_tex_a;
 out vec2 v_tex_b;
 out float v_gamma_scale;
+#ifdef GLOBE
+out float v_depth;
+#endif
 
 #pragma mapbox: define highp vec4 color
 #pragma mapbox: define lowp float blur
@@ -87,6 +90,9 @@ void main() {
     vec4 projected_no_extrude = projectTile(pos + offset2 / u_ratio * adjustedThickness + u_translation);
     vec4 projected_with_extrude = projectTile(pos + offset2 / u_ratio * adjustedThickness + u_translation + dist / u_ratio * adjustedThickness);
     gl_Position = projected_with_extrude;
+    #ifdef GLOBE
+    v_depth = gl_Position.z / gl_Position.w;
+    #endif
 
     // calculate how much the perspective view squishes or stretches the extrude
     #ifdef TERRAIN3D