only animate when we need to fade the text

3 files changed, 36 insertions, 1 deletions

diff --git a/src/map/map.cpp b/src/map/map.cpp
index 078fe01b92..75bfdb2c9e 100644
--- a/src/map/map.cpp
+++ b/src/map/map.cpp
@@ -483,5 +483,5 @@ bool Map::render() {
 
     painter.renderMatte();
 
-    return changed || transform.needsAnimation();
+    return changed || transform.needsAnimation() || painter.needsAnimation();
 }
diff --git a/src/renderer/frame_history.cpp b/src/renderer/frame_history.cpp
index de65c1ad4a..ba0cf56c70 100644
--- a/src/renderer/frame_history.cpp
+++ b/src/renderer/frame_history.cpp
@@ -14,3 +14,34 @@ void FrameHistory::record(float zoom) {
         history.emplace_back(FrameSnapshot{static_cast<float>(platform::time() * 1000), zoom});
     }
 }
+
+bool FrameHistory::needsAnimation(const float duration) const {
+    if (!history.size()) return true;
+
+    // If we have a value that is older than duration and whose z value is the
+    // same as the most current z value, and if all values inbetween have the
+    // same z value, we don't need animation, otherwise we probably do.
+    const FrameSnapshot &pivot = history.back();
+
+    int i = -1;
+    while (history.size() > i + 1 &&
+           history[i + 1].time + duration < pivot.time) {
+        i++;
+    }
+
+    if (i < 0) {
+        // There is no frame that is older than the duration time, so we need to
+        // check all frames.
+        i = 0;
+    }
+
+    // Make sure that all subsequent snapshots have the same zoom as the last
+    // pivot element.
+    for (; history.size() > i; i++) {
+        if (history[i].z != pivot.z) {
+            return true;
+        }
+    }
+
+    return false;
+}
\ No newline at end of file
diff --git a/src/renderer/painter.cpp b/src/renderer/painter.cpp
index 95017465c3..9a52cb36d3 100644
--- a/src/renderer/painter.cpp
+++ b/src/renderer/painter.cpp
@@ -29,6 +29,10 @@ Painter::Painter(Transform& transform, Settings& settings, Style& style, GlyphAt
       glyphAtlas(glyphAtlas) {
 }
 
+bool Painter::needsAnimation() const {
+    return frameHistory.needsAnimation(300);
+}
+
 void Painter::setup() {
     setupShaders();