SCI32: Improve kPlayVMD rendering

1. Added a new game option for linear interpolation when scaling
   overlay-mode video in ScummVM builds with USE_RGB_COLOR;
2. Implemented SCI2.1-variant of the VMD player renderer (fixes
   Trac#9857), which bypasses the engine's normal rendering
   pipeline;
3. Improved accuracy of the SCI3-variant of the VMD player by
   writing HunkPalettes into the VMD's CelObjMem instead of
   submitting palettes directly to GfxPalette32.

1 files changed, 27 insertions, 0 deletions

diff --git a/engines/sci/graphics/palette32.h b/engines/sci/graphics/palette32.h
index fb0b226130..b8ba85eb4a 100644
--- a/engines/sci/graphics/palette32.h
+++ b/engines/sci/graphics/palette32.h
@@ -37,6 +37,16 @@ class HunkPalette {
 public:
 	HunkPalette(const SciSpan<const byte> &rawPalette);
 
+	static void write(SciSpan<byte> &out, const Palette &palette);
+
+	static uint32 calculateHunkPaletteSize(const uint16 numIndexes = 256, const bool sharedUsed = true) {
+		const int numPalettes = 1;
+		return kHunkPaletteHeaderSize +
+			/* slack bytes between hunk header & palette offset table */ 2 +
+			/* palette offset table */ 2 * numPalettes +
+			/* palette data */ (kEntryHeaderSize + numIndexes * (/* RGB */ 3 + !sharedUsed)) * numPalettes;
+	}
+
 	/**
 	 * Gets the version of the palette. Used to avoid resubmitting a HunkPalette
 	 * which has already been submitted for the next frame.
@@ -237,6 +247,14 @@ public:
 	 */
 	inline const Palette &getCurrentPalette() const { return _currentPalette; };
 
+#ifdef USE_RGB_COLOR
+	/**
+	 * Gets the raw hardware palette in RGB format. This should be used instead
+	 * of `::PaletteManager::grabPalette` when the OSystem screen is >8bpp.
+	 */
+	inline const uint8 *getHardwarePalette() const { return _hardwarePalette; };
+#endif
+
 	/**
 	 * Loads a palette into GfxPalette32 with the given resource ID.
 	 */
@@ -288,6 +306,15 @@ private:
 	 */
 	bool _needsUpdate;
 
+#ifdef USE_RGB_COLOR
+	/**
+	 * A local copy of the hardware palette. Used when the backend is in a true
+	 * color mode and a change to the game's internal framebuffer occurs that
+	 * needs to be reconverted from 8bpp to the backend's bit depth.
+	 */
+	uint8 _hardwarePalette[256 * 3];
+#endif
+
 	/**
 	 * The currently displayed palette.
 	 */