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Emoticon Pixmap Caching System

Overview

This document describes the centralized emoticon pixmap caching system in GuiThumbMgr that eliminates the ~10 second delay when opening emoticon-using features.

Problem

Loading 50 emoticon SVGs synchronously takes ~10 seconds. This delay occurred when opening: - InputFaceWidget (face picker in chat) - AppletGalleryEmoticon - Random Person Connect - Any feature needing emoticon pixmaps

Previously, each consumer loaded SVGs independently and synchronously.

Solution

Centralize emoticon pixmap storage in GuiThumbMgr with: 1. 48×48 base pixmaps cached in memory 2. Background loading after login via QTimer
3. Fast path: Load from existing .nlt files (created by gallery system) 4. Slow path: Load from SVG resources (first time only) 5. On-demand scaling: Return scaled copies from the 48×48 cache

Architecture

Cache Storage (GuiThumbMgr)

// 48x48 pixmap cache
static constexpr int kEmoticonCacheSize = 48;
static constexpr int kEmoticonCount = 50;
std::vector<QPixmap> m_EmoticonPixmapCache;  // 50 cached pixmaps
std::vector<bool>    m_EmoticonLoaded;       // tracking flags
bool                 m_EmoticonCacheReady;   // all loaded flag

Loading Flow

  1. Login completion → onSystemReady(true) → startEmoticonCacheLoad()
  2. Background loading via QTimer: 5 emoticons per 50ms tick
  3. For each emoticon:
  4. Try loading from .nlt file (fast - these are PNG files)
  5. Fallback: Load from SVG resource (slow)
  6. Scale to 48×48 and store in cache
  7. When complete: m_EmoticonCacheReady = true, emit signalEmoticonCacheReady()

.nlt File Strategy

  • Cache does NOT write .nlt files - only reads them if they exist
  • Gallery system (generateEmoticon()) creates full-size 240×240 .nlt files
  • If user opens gallery first → .nlt files are created → cache benefits from fast path
  • If user opens face picker first → cache loads from SVG (slower, but only once per session)

Public API

// Get single emoticon scaled to requested size
bool getEmoticonPixmap(int emoticonNum, QSize imageSize, QPixmap& retPixmap);

// Get all 50 emoticons scaled to requested size
bool getAllEmoticonPixmaps(QSize imageSize, QVector<QPixmap>& retPixmaps);

// Check if background loading is complete
bool isEmoticonCacheReady() const;

// Manually trigger background loading (called automatically on login)
void startEmoticonCacheLoad();

// Signal emitted when cache is ready
void signalEmoticonCacheReady();

Consumer Changes

InputFaceWidget

  • Removed SVG loading from constructor
  • Uses getEmoticonPixmap() in refreshScaledPixmaps()
  • Loads pixmaps on-demand from cache (near-instant if cache ready)

Legacy API

getEmoticonImage() now redirects to getEmoticonPixmap() for backward compatibility.

AppletGalleryEmoticon

  • Uses existing generateEmoticonsIfNeeded() flow (creates full-size .nlt files)
  • Gallery thumbnails are 240×240 loaded directly from SVG for quality
  • Once .nlt files exist, other features (like InputFaceWidget) benefit from fast loading

Performance Characteristics

Scenario Time
First session, open face picker early ~10s (loads SVGs in background)
Subsequent face picker opens (same session) Instant (cached)
After gallery has been opened once (creates .nlt files) Fast (~1s to load PNGs)

Design Decisions

  • 48×48 cache size: Good balance of quality vs memory (~200KB total)
  • FastTransformation: Prioritizes speed over quality for scaling
  • QTimer chunked loading: Avoids UI freeze during background load
  • No cache invalidation: Emoticons are only added, never changed
  • Separate gallery path: Gallery uses SVG directly for 240×240 quality

Files Modified