Enable property functions for icon-size

debug/textsize.html

@@ -40,13 +40,19 @@
         "text-anchor": "left",
         "text-allow-overlap": true,
         "text-ignore-placement": true,
+        "icon-allow-overlap": true,
+        "icon-ignore-placement": true,
         "text-max-angle": 180,
         "text-field": "abcdefghijklmnopqrstuvwxyz",
         "text-font": [
             "Open Sans Semibold",
             "Arial Unicode MS Bold"
         ],
-        "text-size": textSize
+        "text-size": textSize,
+        "icon-size": Object.assign({}, textSize, {
+            stops: textSize.stops.map(s => [s[0], s[1] / 3])
+        }),
+        "icon-image": "airfield-11"
     },
     "paint": {
         "text-color": color,
@@ -85,7 +91,7 @@
             }
         }
     },
-
+    "sprite": "mapbox://sprites/mapbox/streets-v10",
     "glyphs": "mapbox://fonts/mapbox/{fontstack}/{range}.pbf",
     "layers": [
         layer('symbol-camera', 0, {

src/shaders/symbol_icon.vertex.glsl

@@ -3,11 +3,20 @@ attribute vec4 a_pos_offset;
 attribute vec2 a_texture_pos;
 attribute vec4 a_data;
 
+// icon-size data (see symbol_sdf.vertex.glsl for more)
+attribute vec3 a_size;
+uniform bool u_is_size_zoom_constant;
+uniform bool u_is_size_feature_constant;
+uniform mediump float u_size_t; // used to interpolate between zoom stops when size is a composite function
+uniform mediump float u_size; // used when size is both zoom and feature constant
+uniform mediump float u_layout_size; // used when size is feature constant
+
 #pragma mapbox: define lowp float opacity
 
 // matrix is for the vertex position.
 uniform mat4 u_matrix;
 
+uniform bool u_is_text;
 uniform mediump float u_zoom;
 uniform bool u_rotate_with_map;
 uniform vec2 u_extrude_scale;
@@ -29,10 +38,38 @@ void main() {
     mediump float a_minzoom = a_zoom[0];
     mediump float a_maxzoom = a_zoom[1];
 
-    // u_zoom is the current zoom level adjusted for the change in font size
-    mediump float z = 2.0 - step(a_minzoom, u_zoom) - (1.0 - step(a_maxzoom, u_zoom));
+    float size;
+    // In order to accommodate placing labels around corners in
+    // symbol-placement: line, each glyph in a label could have multiple
+    // "quad"s only one of which should be shown at a given zoom level.
+    // The min/max zoom assigned to each quad is based on the font size at
+    // the vector tile's zoom level, which might be different than at the
+    // currently rendered zoom level if text-size is zoom-dependent.
+    // Thus, we compensate for this difference by calculating an adjustment
+    // based on the scale of rendered text size relative to layout text size.
+    mediump float layoutSize;
+    if (!u_is_size_zoom_constant && !u_is_size_feature_constant) {
+        size = mix(a_size[0], a_size[1], u_size_t) / 10.0;
+        layoutSize = a_size[2] / 10.0;
+    } else if (u_is_size_zoom_constant && !u_is_size_feature_constant) {
+        size = a_size[0] / 10.0;
+        layoutSize = size;
+    } else if (!u_is_size_zoom_constant && u_is_size_feature_constant) {
+        size = u_size;
+        layoutSize = u_layout_size;
+    } else {
+        size = u_size;
+        layoutSize = u_size;
+    }
+
+    float fontScale = u_is_text ? size / 24.0 : size;
+
+    mediump float zoomAdjust = log2(size / layoutSize);
+    mediump float adjustedZoom = (u_zoom - zoomAdjust) * 10.0;
+    // result: z = 0 if a_minzoom <= adjustedZoom < a_maxzoom, and 1 otherwise
+    mediump float z = 2.0 - step(a_minzoom, adjustedZoom) - (1.0 - step(a_maxzoom, adjustedZoom));
 
-    vec2 extrude = u_extrude_scale * (a_offset / 64.0);
+    vec2 extrude = fontScale * u_extrude_scale * (a_offset / 64.0);
     if (u_rotate_with_map) {
         gl_Position = u_matrix * vec4(a_pos + extrude, 0, 1);
         gl_Position.z += z * gl_Position.w;

src/style-spec/reference/v8.json

@@ -810,6 +810,7 @@
       "minimum": 0,
       "function": "interpolated",
       "zoom-function": true,
+      "property-function": true,
       "doc": "Scale factor for icon. 1 is original size, 3 triples the size.",
       "requires": [
         "icon-image"