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+#include <mbgl/layout/symbol_projection.hpp>
+#include <mbgl/map/transform_state.hpp>
+#include <mbgl/renderer/render_tile.hpp>
+#include <mbgl/renderer/buckets/symbol_bucket.hpp>
+#include <mbgl/renderer/layers/render_symbol_layer.hpp>
+#include <mbgl/renderer/frame_history.hpp>
+#include <mbgl/util/optional.hpp>
+#include <mbgl/util/math.hpp>
+
+namespace mbgl {
+
+ /*
+ * # Overview of coordinate spaces
+ *
+ * ## Tile coordinate spaces
+ * Each label has an anchor. Some labels have corresponding line geometries.
+ * The points for both anchors and lines are stored in tile units. Each tile has it's own
+ * coordinate space going from (0, 0) at the top left to (EXTENT, EXTENT) at the bottom right.
+ *
+ * ## GL coordinate space
+ * At the end of everything, the vertex shader needs to produce a position in GL coordinate space,
+ * which is (-1, 1) at the top left and (1, -1) in the bottom right.
+ *
+ * ## Map pixel coordinate spaces
+ * Each tile has a pixel coordinate space. It's just the tile units scaled so that one unit is
+ * whatever counts as 1 pixel at the current zoom.
+ * This space is used for pitch-alignment=map, rotation-alignment=map
+ *
+ * ## Rotated map pixel coordinate spaces
+ * Like the above, but rotated so axis of the space are aligned with the viewport instead of the tile.
+ * This space is used for pitch-alignment=map, rotation-alignment=viewport
+ *
+ * ## Viewport pixel coordinate space
+ * (0, 0) is at the top left of the canvas and (pixelWidth, pixelHeight) is at the bottom right corner
+ * of the canvas. This space is used for pitch-alignment=viewport
+ *
+ *
+ * # Vertex projection
+ * It goes roughly like this:
+ * 1. project the anchor and line from tile units into the correct label coordinate space
+ * - map pixel space pitch-alignment=map rotation-alignment=map
+ * - rotated map pixel space pitch-alignment=map rotation-alignment=viewport
+ * - viewport pixel space pitch-alignment=viewport rotation-alignment=*
+ * 2. if the label follows a line, find the point along the line that is the correct distance from the anchor.
+ * 3. add the glyph's corner offset to the point from step 3
+ * 4. convert from the label coordinate space to gl coordinates
+ *
+ * For horizontal labels we want to do step 1 in the shader for performance reasons (no cpu work).
+ * This is what `u_label_plane_matrix` is used for.
+ * For labels aligned with lines we have to steps 1 and 2 on the cpu since we need access to the line geometry.
+ * This is what `updateLineLabels(...)` does.
+ * Since the conversion is handled on the cpu we just set `u_label_plane_matrix` to an identity matrix.
+ *
+ * Steps 3 and 4 are done in the shaders for all labels.
+ */
+
+ /*
+ * Returns a matrix for converting from tile units to the correct label coordinate space.
+ */
+ mat4 getLabelPlaneMatrix(const mat4& posMatrix, const bool pitchWithMap, const bool rotateWithMap, const TransformState& state, const float pixelsToTileUnits) {
+ mat4 m;
+ matrix::identity(m);
+ if (pitchWithMap) {
+ matrix::scale(m, m, 1 / pixelsToTileUnits, 1 / pixelsToTileUnits, 1);
+ if (!rotateWithMap) {
+ matrix::rotate_z(m, m, state.getAngle());
+ }
+ } else {
+ matrix::scale(m, m, state.getSize().width / 2.0, -(state.getSize().height / 2.0), 1.0);
+ matrix::translate(m, m, 1, -1, 0);
+ matrix::multiply(m, m, posMatrix);
+ }
+ return m;
+ }
+
+ /*
+ * Returns a matrix for converting from the correct label coordinate space to gl coords.
+ */
+ mat4 getGlCoordMatrix(const mat4& posMatrix, const bool pitchWithMap, const bool rotateWithMap, const TransformState& state, const float pixelsToTileUnits) {
+ mat4 m;
+ matrix::identity(m);
+ if (pitchWithMap) {
+ matrix::multiply(m, m, posMatrix);
+ matrix::scale(m, m, pixelsToTileUnits, pixelsToTileUnits, 1);
+ if (!rotateWithMap) {
+ matrix::rotate_z(m, m, -state.getAngle());
+ }
+ } else {
+ matrix::scale(m, m, 1, -1, 1);
+ matrix::translate(m, m, -1, -1, 0);
+ matrix::scale(m, m, 2.0 / state.getSize().width, 2.0 / state.getSize().height, 1.0);
+ }
+ return m;
+ }
+
+
+ Point<float> project(const Point<float>& point, const mat4& matrix) {
+ vec4 pos = {{ point.x, point.y, 0, 1 }};
+ matrix::transformMat4(pos, pos, matrix);
+ return { static_cast<float>(pos[0] / pos[3]), static_cast<float>(pos[1] / pos[3]) };
+ }
+
+ float evaluateSizeForFeature(const ZoomEvaluatedSize& zoomEvaluatedSize, const PlacedSymbol& placedSymbol) {
+ if (zoomEvaluatedSize.isFeatureConstant) {
+ return zoomEvaluatedSize.size;
+ } else {
+ if (zoomEvaluatedSize.isZoomConstant) {
+ return placedSymbol.lowerSize;
+ } else {
+ return placedSymbol.lowerSize + zoomEvaluatedSize.sizeT * (placedSymbol.upperSize - placedSymbol.lowerSize);
+ }
+ }
+ }
+
+ bool isVisible(const vec4& anchorPos, const float placementZoom, const std::array<double, 2>& clippingBuffer, const FrameHistory& frameHistory) {
+ const float x = anchorPos[0] / anchorPos[3];
+ const float y = anchorPos[1] / anchorPos[3];
+ const bool inPaddedViewport = (
+ x >= -clippingBuffer[0] &&
+ x <= clippingBuffer[0] &&
+ y >= -clippingBuffer[1] &&
+ y <= clippingBuffer[1]);
+ return inPaddedViewport && frameHistory.isVisible(placementZoom);
+ }
+
+ void addDynamicAttributes(const Point<float>& anchorPoint, const float angle, const float placementZoom,
+ gl::VertexVector<SymbolDynamicLayoutAttributes::Vertex>& dynamicVertexArray) {
+ auto dynamicVertex = SymbolDynamicLayoutAttributes::vertex(anchorPoint, angle, placementZoom);
+ dynamicVertexArray.emplace_back(dynamicVertex);
+ dynamicVertexArray.emplace_back(dynamicVertex);
+ dynamicVertexArray.emplace_back(dynamicVertex);
+ dynamicVertexArray.emplace_back(dynamicVertex);
+ }
+
+ void hideGlyphs(size_t numGlyphs, gl::VertexVector<SymbolDynamicLayoutAttributes::Vertex>& dynamicVertexArray) {
+ const Point<float> offscreenPoint = { -INFINITY, -INFINITY };
+ for (size_t i = 0; i < numGlyphs; i++) {
+ addDynamicAttributes(offscreenPoint, 0, 25, dynamicVertexArray);
+ }
+ }
+
+ struct PlacedGlyph {
+ PlacedGlyph(Point<float> point_, float angle_) : point(point_), angle(angle_) {}
+ Point<float> point;
+ float angle;
+ };
+
+ optional<PlacedGlyph> placeGlyphAlongLine(const float offsetX, const float lineOffsetX, const float lineOffsetY, const bool flip,
+ Point<float> anchorPoint, const uint16_t anchorSegment, const GeometryCoordinates& line, const mat4& labelPlaneMatrix) {
+
+ const float combinedOffsetX = flip ?
+ offsetX - lineOffsetX :
+ offsetX + lineOffsetX;
+
+ int16_t dir = combinedOffsetX > 0 ? 1 : -1;
+
+ float angle = 0.0;
+ if (flip) {
+ // The label needs to be flipped to keep text upright.
+ // Iterate in the reverse direction.
+ dir *= -1;
+ angle = M_PI;
+ }
+
+ if (dir < 0) angle += M_PI;
+
+ int32_t currentIndex = dir > 0 ? anchorSegment : anchorSegment + 1;
+
+ Point<float> current = anchorPoint;
+ Point<float> prev = anchorPoint;
+ float distanceToPrev = 0.0;
+ float currentSegmentDistance = 0.0;
+ const float absOffsetX = std::abs(combinedOffsetX);
+
+ while (distanceToPrev + currentSegmentDistance <= absOffsetX) {
+ currentIndex += dir;
+
+ // offset does not fit on the projected line
+ if (currentIndex < 0 || currentIndex >= static_cast<int32_t>(line.size())) return {};
+
+ prev = current;
+ current = project(convertPoint<float>(line.at(currentIndex)), labelPlaneMatrix);
+
+ distanceToPrev += currentSegmentDistance;
+ currentSegmentDistance = util::dist<float>(prev, current);
+ }
+
+ // The point is on the current segment. Interpolate to find it.
+ const float segmentInterpolationT = (absOffsetX - distanceToPrev) / currentSegmentDistance;
+ const Point<float> prevToCurrent = current - prev;
+ Point<float> p = (prevToCurrent * segmentInterpolationT) + prev;
+
+ // offset the point from the line to text-offset and icon-offset
+ p += util::perp(prevToCurrent) * static_cast<float>(lineOffsetY * dir / util::mag(prevToCurrent));
+
+ const float segmentAngle = angle + std::atan2(current.y - prev.y, current.x - prev.x);
+
+ return {{ p, segmentAngle }};
+ }
+
+ void placeGlyphsAlongLine(const PlacedSymbol& symbol, const float fontSize, const bool flip, const mat4& labelPlaneMatrix,
+ gl::VertexVector<SymbolDynamicLayoutAttributes::Vertex>& dynamicVertexArray) {
+ const float fontScale = fontSize / 24.0;
+ const float lineOffsetX = symbol.lineOffset[0] * fontSize;
+ const float lineOffsetY = symbol.lineOffset[1] * fontSize;
+
+ const Point<float> anchorPoint = project(symbol.anchorPoint, labelPlaneMatrix);
+
+ std::vector<PlacedGlyph> placedGlyphs;
+ for (auto glyphOffsetX : symbol.glyphOffsets) {
+ auto placedGlyph = placeGlyphAlongLine(glyphOffsetX * fontScale, lineOffsetX, lineOffsetY, flip, anchorPoint, symbol.segment, symbol.line, labelPlaneMatrix);
+ if (placedGlyph) {
+ placedGlyphs.push_back(*placedGlyph);
+ } else {
+ hideGlyphs(symbol.glyphOffsets.size(), dynamicVertexArray);
+ return;
+ }
+ }
+
+ for (auto& placedGlyph : placedGlyphs) {
+ addDynamicAttributes(placedGlyph.point, placedGlyph.angle, symbol.placementZoom, dynamicVertexArray);
+ }
+ }
+
+ void reprojectLineLabels(gl::VertexVector<SymbolDynamicLayoutAttributes::Vertex>& dynamicVertexArray, const std::vector<PlacedSymbol>& placedSymbols,
+ const mat4& posMatrix, const style::SymbolPropertyValues& values,
+ const RenderTile& tile, const SymbolSizeBinder& sizeBinder, const TransformState& state, const FrameHistory& frameHistory) {
+
+ const ZoomEvaluatedSize partiallyEvaluatedSize = sizeBinder.evaluateForZoom(state.getZoom());
+
+ const std::array<double, 2> clippingBuffer = {{ 256.0 / state.getSize().width * 2.0 + 1.0, 256.0 / state.getSize().height * 2.0 + 1.0 }};
+
+ const mat4 labelPlaneMatrix = getLabelPlaneMatrix(posMatrix, values.pitchAlignment == style::AlignmentType::Map,
+ values.rotationAlignment == style::AlignmentType::Map, state, tile.id.pixelsToTileUnits(1, state.getZoom()));
+
+ dynamicVertexArray.clear();
+
+ for (auto& placedSymbol : placedSymbols) {
+ vec4 anchorPos = {{ placedSymbol.anchorPoint.x, placedSymbol.anchorPoint.y, 0, 1 }};
+ matrix::transformMat4(anchorPos, anchorPos, posMatrix);
+
+ // Don't bother calculating the correct point for invisible labels.
+ if (!isVisible(anchorPos, placedSymbol.placementZoom, clippingBuffer, frameHistory)) {
+ hideGlyphs(placedSymbol.glyphOffsets.size(), dynamicVertexArray);
+ continue;
+ }
+
+ bool flip = false;
+ if (values.keepUpright) {
+ const Point<float> a = project(convertPoint<float>(placedSymbol.line.at(placedSymbol.segment)), posMatrix);
+ const Point<float> b = project(convertPoint<float>(placedSymbol.line.at(placedSymbol.segment + 1)), posMatrix);
+ flip = placedSymbol.useVerticalMode ? b.y > a.y : b.x < a.x;
+ }
+
+ const float cameraToAnchorDistance = anchorPos[3];
+ const float perspectiveRatio = 1 + 0.5 * ((cameraToAnchorDistance / state.getCameraToCenterDistance()) - 1.0);
+
+ const float fontSize = evaluateSizeForFeature(partiallyEvaluatedSize, placedSymbol);
+ const float pitchScaledFontSize = values.pitchAlignment == style::AlignmentType::Map ?
+ fontSize * perspectiveRatio :
+ fontSize / perspectiveRatio;
+
+ placeGlyphsAlongLine(placedSymbol, pitchScaledFontSize, flip, labelPlaneMatrix, dynamicVertexArray);
+ }
+ }
+} // end namespace mbgl
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