[kandinsky] Introduce a KDFont class

kandinsky/Makefile

@@ -6,6 +6,8 @@ objs += $(addprefix kandinsky/src/,\
   context_pixel.o\
   context_rect.o\
   context_text.o\
+  font.o\
+  font_small.o\
   framebuffer.o\
   framebuffer_context.o\
   ion_context.o\

kandinsky/src/font.cpp

@@ -0,0 +1,55 @@
+#include "font.h"
+#include <assert.h>
+
+void decompress(const uint8_t * source, int sourceLength, uint8_t * output, int outputLength);
+
+void KDFont::fetchGreyscaleGlyphForChar(char c, uint8_t * greyscaleBuffer) const {
+  decompress(
+    compressedGlyphData(c),
+    compressedGlyphDataSize(c),
+    greyscaleBuffer,
+    m_glyphWidth*m_glyphHeight
+  );
+}
+
+void KDFont::fetchGlyphForChar(char c, const KDFont::RenderPalette & renderPalette, KDColor * pixelBuffer) const {
+  /* Since a greyscale value is smaller than a color value (see assertion), we
+   * can store the temporary greyscale values in the output pixel buffer.
+   * What's great is that now, if we fill the pixel buffer right-to-left with
+   * colors derived from the temporary greyscale values, we will never overwrite
+   * the remaining grayscale values since those are smaller. So we can avoid a
+   * separate buffer for the temporary greyscale values. */
+  assert(k_bitsPerPixel < 8*sizeof(KDColor));
+  uint8_t * greyscaleBuffer = reinterpret_cast<uint8_t *>(pixelBuffer);
+  fetchGreyscaleGlyphForChar(c, greyscaleBuffer);
+
+  int numberOfPixels = m_glyphWidth*m_glyphHeight;
+  uint8_t mask = (0xFF >> (8-k_bitsPerPixel));
+  int pixelIndex = m_glyphWidth * m_glyphHeight;
+  int greyscaleByteIndex = pixelIndex / k_bitsPerPixel;
+  while (pixelIndex >= 0) {
+    uint8_t greyscaleByte = greyscaleBuffer[greyscaleByteIndex--];
+    assert(greyscaleByteIndex >= 0);
+    for (int j=0; j<8/k_bitsPerPixel; j++) {
+      uint8_t greyscale = greyscaleByte & mask;
+      greyscaleByte = greyscaleByte >> k_bitsPerPixel;
+      pixelBuffer[pixelIndex--] = renderPalette.colorAtIndex(greyscale);
+    }
+  }
+}
+
+constexpr int glyphPixelCount = 12;
+
+void drawString(const char * text, KDColor textColor, KDColor backgroundColor) {
+  const KDFont * font = KDFont::LargeFont;
+  KDFont::RenderPalette palette = font->renderPalette(textColor, backgroundColor);
+
+  assert(glyphPixelCount >= font->glyphWidth() * font->glyphHeight());
+
+  char c;
+  do {
+    char c = text[0];
+    KDColor glyph[glyphPixelCount];
+    font->fetchGlyphForChar(c, palette, glyph);
+  } while (c != 0);
+}

kandinsky/src/font_small.cpp

@@ -0,0 +1,22 @@
+#include "font.h"
+
+static constexpr KDCoordinate glyphWidth = 8;
+
+static constexpr KDCoordinate glyphHeight = 8;
+
+static constexpr uint16_t glyphDataOffset[] = {
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
+};
+
+static constexpr uint8_t glyphData[] = {
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+  0x00
+};
+
+constexpr KDFont font(glyphWidth, glyphHeight, glyphDataOffset, glyphData);
+
+const KDFont * KDFont::SmallFont = &font;

kandinsky/src/palette.h

@@ -0,0 +1,24 @@
+#ifndef KANDINSKY_PALETTE_H
+#define KANDINSKY_PALETTE_H
+
+#include <kandinsky/color.h>
+
+template <int S>
+class KDPalette {
+public:
+  static KDPalette Gradient(KDColor fromColor, KDColor toColor) {
+    KDPalette p;
+    for (int i=0; i<S; i++) {
+      p.m_colors[i] = KDColor::blend(fromColor, toColor, (0xFF*i)/S);
+    }
+    return p;
+  }
+  KDColor colorAtIndex(int i) const {
+    return m_colors[i];
+  }
+private:
+  KDPalette() {}
+  KDColor m_colors[S];
+};
+
+#endif