IconCache: Add pending state to avoid duplicate downloads in some cases

Common/UI/IconCache.cpp

@@ -33,12 +33,10 @@ void IconCache::SaveToFile(FILE *file) {
 	DiskCacheHeader header;
 	header.magic = ICON_CACHE_MAGIC;
 	header.version = ICON_CACHE_VERSION;
-	header.entryCount = 0;  // (uint32_t)cache_.size();
+	header.entryCount = (uint32_t)cache_.size();
 
 	fwrite(&header, 1, sizeof(header), file);
 
-	return;
-
 	for (auto &iter : cache_) {
 		DiskCacheEntry entryHeader;
 		entryHeader.keyLen = (uint32_t)iter.first.size();
@@ -142,6 +140,23 @@ bool IconCache::Contains(const std::string &key) {
 	return cache_.find(key) != cache_.end();
 }
 
+bool IconCache::MarkPending(const std::string &key) {
+	std::unique_lock<std::mutex> lock(lock_);
+	if (cache_.find(key) != cache_.end()) {
+		return false;
+	}
+	if (pending_.find(key) != pending_.end()) {
+		return false;
+	}
+	pending_.insert(key);
+	return true;
+}
+
+void IconCache::Cancel(const std::string &key) {
+	std::unique_lock<std::mutex> lock(lock_);
+	pending_.erase(key);
+}
+
 bool IconCache::InsertIcon(const std::string &key, IconFormat format, std::string &&data) {
 	std::unique_lock<std::mutex> lock(lock_);
 
@@ -159,6 +174,8 @@ bool IconCache::InsertIcon(const std::string &key, IconFormat format, std::strin
 		return false;
 	}
 
+	pending_.erase(key);
+
 	double now = time_now_d();
 	cache_.emplace(key, Entry{ std::move(data), format, nullptr, now, now, false });
 	return true;
@@ -238,5 +255,7 @@ IconCacheStats IconCache::GetStats() {
 		stats.dataSize += iter.second.data.size();
 	}
 
+	stats.pending = pending_.size();
+
 	return stats;
 }

Common/UI/IconCache.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include <map>
+#include <set>
 #include <string>
 #include <cstdio>
 #include <mutex>
@@ -23,6 +24,7 @@ class Texture;
 struct IconCacheStats {
 	size_t cachedCount;
 	size_t textureCount;  // number of cached images that are "live" textures
+	size_t pending;
 	size_t dataSize;
 };
 
@@ -30,7 +32,9 @@ class IconCache {
 public:
 	Draw::Texture *BindIconTexture(UIContext *context, const std::string &key);
 
-	// It's okay to call this from any thread.
+	// It's okay to call these from any thread.
+	bool MarkPending(const std::string &key);  // returns false if already pending or loaded
+	void Cancel(const std::string &key);
 	bool InsertIcon(const std::string &key, IconFormat format, std::string &&pngData);
 	bool GetDimensions(const std::string &key, int *width, int *height);
 	bool Contains(const std::string &key);
@@ -56,6 +60,7 @@ private:
 	void Decimate();
 
 	std::map<std::string, Entry> cache_;
+	std::set<std::string> pending_;
 
 	std::mutex lock_;
 };

UI/Store.cpp

@@ -56,12 +56,16 @@ public:
 	HttpImageFileView(http::Downloader *downloader, const std::string &path, UI::ImageSizeMode sizeMode = UI::IS_DEFAULT, bool useIconCache = true, UI::LayoutParams *layoutParams = nullptr)
 		: UI::View(layoutParams), path_(path), sizeMode_(sizeMode), downloader_(downloader), useIconCache_(useIconCache) {
 
-		if (useIconCache && !g_iconCache.Contains(path_)) {
+		if (useIconCache && g_iconCache.MarkPending(path_)) {
 			const char *acceptMime = "image/png, image/jpeg, image/*; q=0.9, */*; q=0.8";
 			downloader_->StartDownloadWithCallback(path_, Path(), [&](http::Download &download) {
-				std::string data;
-				download.buffer().TakeAll(&data);
-				g_iconCache.InsertIcon(path_, IconFormat::PNG, std::move(data));
+				if (download.ResultCode() == 200) {
+					std::string data;
+					download.buffer().TakeAll(&data);
+					g_iconCache.InsertIcon(path_, IconFormat::PNG, std::move(data));
+				} else {
+					g_iconCache.Cancel(path_);
+				}
 			}, acceptMime);
 		}
 	}