71 lines
2.9 KiB
C#
71 lines
2.9 KiB
C#
using System;
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using System.Collections.Generic;
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using System.Globalization;
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using System.IO;
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using Avalonia.Data.Converters;
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using Avalonia.Media.Imaging;
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namespace LANCommander.Launcher.Converters;
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/// <summary>
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/// Converts a file path string to a thumbnail Bitmap.
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/// Decodes at a fixed width so full-resolution source images don't consume
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/// excessive memory, and caches bitmaps via WeakReference so they are freed
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/// by the GC once no control is displaying them (e.g. after virtualization
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/// scrolls them out of view) and reloaded on next access.
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/// </summary>
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public class FilePathToBitmapConverter : IValueConverter
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{
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// Covers are displayed at 140–220 px wide. 320 px gives enough headroom
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// for high-DPI screens while keeping per-image memory around 400 KB
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// instead of several MB for full-resolution sources.
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private const int DecodeWidth = 320;
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// WeakReference cache: keeps bitmaps alive while on-screen, lets the GC
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// collect them once nothing holds a strong reference (i.e. off-screen).
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// Key is "{path}|{decodeWidth}" so full-res and thumbnail don't collide.
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private static readonly Dictionary<string, WeakReference<Bitmap>> _cache = new();
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public static readonly FilePathToBitmapConverter Instance = new();
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public object? Convert(object? value, Type targetType, object? parameter, CultureInfo culture)
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{
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if (value is not string path || string.IsNullOrEmpty(path))
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return null;
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// ConverterParameter="full" → full resolution (e.g. game detail view)
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// ConverterParameter="h{N}" → DecodeToHeight(N) (e.g. carousel backgrounds)
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// default → DecodeToWidth(320)
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bool fullRes = parameter is string p && p == "full";
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int? decodeHeight = parameter is string hp && hp.StartsWith("h") && int.TryParse(hp.AsSpan(1), out var h) ? h : null;
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var cacheKey = fullRes ? $"{path}|full"
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: decodeHeight.HasValue ? $"{path}|h{decodeHeight}"
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: $"{path}|{DecodeWidth}";
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if (_cache.TryGetValue(cacheKey, out var weakRef) && weakRef.TryGetTarget(out var cached))
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return cached;
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try
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{
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if (!File.Exists(path))
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return null;
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using var stream = File.OpenRead(path);
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var bitmap = fullRes
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? new Bitmap(stream)
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: decodeHeight.HasValue
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? Bitmap.DecodeToHeight(stream, decodeHeight.Value, BitmapInterpolationMode.HighQuality)
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: Bitmap.DecodeToWidth(stream, DecodeWidth, BitmapInterpolationMode.HighQuality);
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_cache[cacheKey] = new WeakReference<Bitmap>(bitmap);
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return bitmap;
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}
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catch
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{
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return null;
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}
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}
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public object? ConvertBack(object? value, Type targetType, object? parameter, CultureInfo culture) =>
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throw new NotSupportedException();
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}
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