From 29ea44560d4298c763b127c23c618cc8c009026e Mon Sep 17 00:00:00 2001
From: gaozheng <gaozheng.cn@gmail.com>
Date: Wed, 17 Jun 2026 08:54:20 +0800
Subject: [PATCH] =?UTF-8?q?fix(vtk):=20=E5=BA=95=E5=9B=BELOD=E6=B6=88?=
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---
 src/app/TileBasemap.cpp | 48 +++++++++++++++++++++++++----------------
 src/app/TileBasemap.hpp |  1 +
 2 files changed, 31 insertions(+), 18 deletions(-)

diff --git a/src/app/TileBasemap.cpp b/src/app/TileBasemap.cpp
index 7af4d07..0218950 100644
--- a/src/app/TileBasemap.cpp
+++ b/src/app/TileBasemap.cpp
@@ -38,6 +38,8 @@ constexpr int kRadius = 3;            // 中心瓦片 ±3 → 最多 7x7=49 块
 constexpr int kMinZoom = 3;
 constexpr int kMaxZoom = 18;
 constexpr double kGroundZ = 0.0;      // 底图置于 z=0 地面参考（剖面深度向下为负，落其下）
+constexpr double kZEps = 0.02;        // 每层级 Z 微偏移：高层级压上面，避免共面瓦片 z-fighting
+constexpr int kHardCap = 400;         // 瓦片硬上限：超过则即便未落地也强制清理，兜底内存
 constexpr double kPi = 3.14159265358979323846;
 constexpr double kEarthCirc = 40075016.686;  // 赤道周长(米) = z0 单瓦片地面尺寸
 constexpr double kTilesAcross = 4.0;          // 视野跨度目标覆盖瓦片数（决定层级）
@@ -149,17 +151,7 @@ void TileBasemap::refresh() {
         }
     }
 
-    // 移除离开视野/换层级的瓦片。
-    for (auto it = placed_.begin(); it != placed_.end();) {
-        if (desired_.find(it->first) == desired_.end()) {
-            scene_.renderer()->RemoveViewProp(it->second);
-            it = placed_.erase(it);
-        } else {
-            ++it;
-        }
-    }
-
-    // 拉取缺失瓦片。
+    // 拉取缺失瓦片（旧层暂不删，留作回退；新层落地后由 purgeStale 清理）。
     for (long long key : desired_) {
         if (placed_.count(key) || inFlight_.count(key)) continue;
         int z, x, y;
@@ -167,10 +159,28 @@ void TileBasemap::refresh() {
         fetchTile(z, x, y, key);
     }
 
+    purgeStale();  // 若无需新拉(inFlight 空)则立即清理旧层
     if (rw_) rw_->Render();
     refreshing_ = false;
 }
 
+void TileBasemap::purgeStale() {
+    // 仅当本轮所有请求都落地(inFlight 空)后再删旧层；否则缩放/平移期间老瓦片留作回退，避免空白闪烁。
+    // 超过硬上限则强制清理兜底内存（可能短暂空白，极少触发）。
+    if (!inFlight_.empty() && placed_.size() <= static_cast<size_t>(kHardCap)) return;
+    bool removed = false;
+    for (auto it = placed_.begin(); it != placed_.end();) {
+        if (desired_.find(it->first) == desired_.end()) {
+            scene_.renderer()->RemoveViewProp(it->second);
+            it = placed_.erase(it);
+            removed = true;
+        } else {
+            ++it;
+        }
+    }
+    if (removed && rw_) rw_->Render();
+}
+
 void TileBasemap::fetchTile(int z, int x, int y, long long key) {
     const QString layerDir = (kind_ == Satellite) ? QStringLiteral("img_w") : QStringLiteral("vec_w");
     const QString layer = (kind_ == Satellite) ? QStringLiteral("img") : QStringLiteral("vec");
@@ -195,11 +205,12 @@ void TileBasemap::fetchTile(int z, int x, int y, long long key) {
         if (gen != generation_) return;                     // 换源/隐藏后丢弃
         if (kind_ == Hidden) return;
         if (desired_.find(key) == desired_.end()) return;   // 已移出视野
-        if (placed_.count(key)) return;
-        if (reply->error() != QNetworkReply::NoError) return;
         QImage img;
-        if (!img.loadFromData(reply->readAll())) return;
-        placeTile(key, z, x, y, img);
+        if (!placed_.count(key) && reply->error() == QNetworkReply::NoError &&
+            img.loadFromData(reply->readAll())) {
+            placeTile(key, z, x, y, img);  // 仅新瓦片落地；其余(失败/已存在)只推动清理
+        }
+        purgeStale();  // 本块已解决 → 若整轮落地则清理被顶替的旧层
     });
 }
 
@@ -208,6 +219,7 @@ void TileBasemap::placeTile(long long key, int z, int x, int y, const QImage& im
     const auto sw = frame_->toLocal(b.south, b.west);
     const auto se = frame_->toLocal(b.south, b.east);
     const auto nw = frame_->toLocal(b.north, b.west);
+    const double gz = kGroundZ + (z - kMinZoom) * kZEps;  // 高层级略抬高，压在旧层之上防共面闪烁
 
     // QImage → vtkImageData(RGBA)，垂直翻转：使纹理 v=0 对应瓦片南边（与下方 PlaneSource tcoord 一致）。
     const QImage rgba = img.convertToFormat(QImage::Format_RGBA8888);
@@ -228,9 +240,9 @@ void TileBasemap::placeTile(long long key, int z, int x, int y, const QImage& im
     // PlaneSource 自动 tcoord：origin→(0,0)、point1→(1,0)、point2→(0,1)。
     //   origin=SW(西南)、point1=SE(东) → u 西→东；point2=NW(北) → v 南→北。与翻转后纹理对齐。
     vtkNew<vtkPlaneSource> plane;
-    plane->SetOrigin(sw.x, sw.y, kGroundZ);
-    plane->SetPoint1(se.x, se.y, kGroundZ);
-    plane->SetPoint2(nw.x, nw.y, kGroundZ);
+    plane->SetOrigin(sw.x, sw.y, gz);
+    plane->SetPoint1(se.x, se.y, gz);
+    plane->SetPoint2(nw.x, nw.y, gz);
 
     vtkNew<vtkPolyDataMapper> mapper;
     mapper->SetInputConnection(plane->GetOutputPort());
diff --git a/src/app/TileBasemap.hpp b/src/app/TileBasemap.hpp
index b0cdf83..b4f23b1 100644
--- a/src/app/TileBasemap.hpp
+++ b/src/app/TileBasemap.hpp
@@ -37,6 +37,7 @@ public:
 private:
     static long long tileKey(int z, int x, int y);
     void ensureObserver();  // 首次显示时挂到交互样式的 EndInteractionEvent
+    void purgeStale();      // 本轮请求全部落地后再删旧层瓦片，避免缩放空白闪烁
     bool computeView(double& centerLat, double& centerLon, int& zoom) const;
     void fetchTile(int z, int x, int y, long long key);
     void placeTile(long long key, int z, int x, int y, const QImage& img);