From 39e1c86ae94f150b5d2a9687ebdd91647c87d11d Mon Sep 17 00:00:00 2001
From: Petr Pokorny <petr-pokorny@hotmail.com>
Date: Sun, 28 Feb 2021 19:01:03 +0100
Subject: [PATCH 1/2] fixes #16

---
 src/mbgl/renderer/layers/render_symbol_layer.cpp |  3 ++-
 src/mbgl/text/placement.cpp                      | 14 +++++++++++---
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/src/mbgl/renderer/layers/render_symbol_layer.cpp b/src/mbgl/renderer/layers/render_symbol_layer.cpp
index 1d8c0a70a..d70d10d6f 100644
--- a/src/mbgl/renderer/layers/render_symbol_layer.cpp
+++ b/src/mbgl/renderer/layers/render_symbol_layer.cpp
@@ -424,7 +424,8 @@ void RenderSymbolLayer::render(PaintParameters& parameters) {
         assert(bucket.paintProperties.find(getID()) != bucket.paintProperties.end());
         const auto& bucketPaintProperties = bucket.paintProperties.at(getID());
 
-        bucket.justReloaded = false;
+        // Prevent a flickering issue when a symbol is moved.
+        // bucket.justReloaded = false;
 
         auto addRenderables = [&renderableSegments, &tile, renderData, &bucketPaintProperties, it = renderableSegments.begin()] (auto& segments, const SymbolType type) mutable {
             for (auto& segment : segments) {
diff --git a/src/mbgl/text/placement.cpp b/src/mbgl/text/placement.cpp
index f98039dec..c3072b05c 100644
--- a/src/mbgl/text/placement.cpp
+++ b/src/mbgl/text/placement.cpp
@@ -241,9 +241,16 @@ void Placement::placeSymbolBucket(const BucketPlacementData& params, std::set<ui
     for (const SymbolInstance& symbol : getSortedSymbols(params, ctx.pixelRatio)) {
         if (seenCrossTileIDs.count(symbol.crossTileID) != 0u) continue;
         placeSymbol(symbol, ctx);
-        seenCrossTileIDs.insert(symbol.crossTileID);
+
+        // Prevent a flickering issue while zooming out.
+        if (symbol.crossTileID != SymbolInstance::invalidCrossTileID() && !ctx.getRenderTile().holdForFade()) {
+            seenCrossTileIDs.insert(symbol.crossTileID);
+        }        
     }
 
+    // Prevent a flickering issue when a symbol is moved.
+    symbolBucket.justReloaded = false;
+
     // As long as this placement lives, we have to hold onto this bucket's
     // matching FeatureIndex/data for querying purposes
     retainedQueryData.emplace(
@@ -905,9 +912,10 @@ void Placement::updateBucketOpacities(SymbolBucket& bucket,
     // But we have to wait for placement if we potentially depend on a paired icon/text
     // with allow-overlap: false.
     // See https://github.com/mapbox/mapbox-gl-native/issues/12483
+    // Prevent a flickering issue when showing a symbol allowing overlap.
     const JointOpacityState defaultOpacityState(
-            textAllowOverlap && (iconAllowOverlap || !(bucket.hasIconData() || bucket.hasSdfIconData()) || bucket.layout->get<style::IconOptional>()),
-            iconAllowOverlap && (textAllowOverlap || !bucket.hasTextData() || bucket.layout->get<style::TextOptional>()),
+            bucket.justReloaded && textAllowOverlap && (iconAllowOverlap || !(bucket.hasIconData() || bucket.hasSdfIconData()) || bucket.layout->get<style::IconOptional>()),
+            bucket.justReloaded && iconAllowOverlap && (textAllowOverlap || !bucket.hasTextData() || bucket.layout->get<style::TextOptional>()),
             true);
 
     for (SymbolInstance& symbolInstance : bucket.symbolInstances) {

From 1b0479c6e586ba797f9420bf102e8d4153494b40 Mon Sep 17 00:00:00 2001
From: Petr Pokorny <petr-pokorny@hotmail.com>
Date: Sun, 28 Feb 2021 19:24:01 +0100
Subject: [PATCH 2/2] Changelog update

---
 platform/android/CHANGELOG.md          | 4 ++++
 platform/ios/platform/ios/CHANGELOG.md | 1 +
 2 files changed, 5 insertions(+)

diff --git a/platform/android/CHANGELOG.md b/platform/android/CHANGELOG.md
index 365a63d9b..051dda106 100644
--- a/platform/android/CHANGELOG.md
+++ b/platform/android/CHANGELOG.md
@@ -6,6 +6,10 @@ Mapbox welcomes participation and contributions from everyone. Please read [`Con
 
 ### Features
 
+### Bug Fixes
+
+* Fixed an issue where symbols flickered when zooming out. [#16](https://github.com/maplibre/maplibre-gl-native/issues/16)
+
 ### Other
 
 * mapbox-gl-js submodule has been replaced with maplibre-gl-js
diff --git a/platform/ios/platform/ios/CHANGELOG.md b/platform/ios/platform/ios/CHANGELOG.md
index 358ece1f6..4baf6ce3b 100644
--- a/platform/ios/platform/ios/CHANGELOG.md
+++ b/platform/ios/platform/ios/CHANGELOG.md
@@ -17,6 +17,7 @@ Mapbox welcomes participation and contributions from everyone. Please read [CONT
 ### Bug Fixes
 
 * Fixed an issue that caused a crash when custom location managers did not implement `MGLLocationManager.accuracyAuthorization`. (cherry pick from [#474](https://github.com/mapbox/mapbox-gl-native-ios/pull/474))
+* Fixed an issue where symbols flickered when zooming out. [#16](https://github.com/maplibre/maplibre-gl-native/issues/16)
 
 ### Other