Add inital console font rendering

src/modules/main/font.c

@@ -0,0 +1,81 @@
+#include "font.h"
+#include "screen.h"
+
+/* PSF2 header format
+ * Taken from the Linux KBD documentation
+ * http://www.win.tue.nl/~aeb/linux/kbd/font-formats-1.html
+ */
+
+const static uint8_t magic[] = {0x72, 0xb5, 0x4a, 0x86};
+
+/* bits used in flags */
+enum psf2_flags {
+	psf2_has_unicode = 0x00000001
+};
+
+/* max version recognized so far */
+#define PSF2_MAXVERSION 0
+
+/* UTF8 separators */
+#define PSF2_SEPARATOR  0xFF
+#define PSF2_STARTSEQ   0xFE
+
+struct psf2_header {
+	uint8_t magic[4];
+	uint32_t version;
+	uint32_t header_size;   // offset of bitmaps in file
+	uint32_t flags;
+	uint32_t length;        // number of glyphs
+	uint32_t charsize;      // number of bytes for each character
+	uint32_t height, width; // max dimensions of glyphs
+};
+
+int
+font_init(void *header, struct font *font)
+{
+	struct psf2_header *psf2 = (struct psf2_header *)header;
+	for (int i = 0; i < sizeof(magic); ++i) {
+		if (psf2->magic[i] != magic[i]) {
+			return 1;
+		}
+	}
+
+	if (font == 0)
+		return 2;
+
+	font->height = psf2->height;
+	font->width = psf2->width;
+	font->charsize = psf2->charsize;
+	font->count = psf2->length;
+	font->data = (uint8_t *)header + psf2->header_size;
+	return 0;
+}
+
+int
+font_draw(
+	struct font *f,
+    struct screen *s,
+    uint32_t glyph,
+	uint32_t color,
+    uint32_t x,
+    uint32_t y)
+{
+	const uint32_t height = f->height;
+	const uint32_t width = f->width;
+	const uint32_t bwidth = (width+7)/8;
+	uint8_t *data = f->data + (glyph * f->charsize);
+
+	for (int dy = 0; dy < f->height; ++dy) {
+		for (int dx = 0; dx < bwidth; ++dx) {
+			uint8_t byte = data[dy * bwidth + dx];
+			for (int i = 0; i < 8; ++i) {
+				if (dx*8 + i >= width) continue;
+				const uint8_t mask = 1 << (7-i);
+				uint32_t c = (byte & mask) ? color : 0;
+				screen_pixel(s, x + dx*8 + i, y + dy, c);
+			}
+		}
+	}
+	return 0;
+}
+

src/modules/main/font.h

@@ -1,32 +1,22 @@
 #pragma once
 #include <stdint.h>
 
-/* PSF2 header format
- * Taken from the Linux KBD documentation
- * http://www.win.tue.nl/~aeb/linux/kbd/font-formats-1.html
- */
+struct screen;
 
-#define PSF2_MAGIC0     0x72
-#define PSF2_MAGIC1     0xb5
-#define PSF2_MAGIC2     0x4a
-#define PSF2_MAGIC3     0x86
-
-/* bits used in flags */
-#define PSF2_HAS_UNICODE_TABLE 0x01
-
-/* max version recognized so far */
-#define PSF2_MAXVERSION 0
-
-/* UTF8 separators */
-#define PSF2_SEPARATOR  0xFF
-#define PSF2_STARTSEQ   0xFE
-
-struct psf2_header {
-	uint8_t magic[4];
-	uint32_t version;
-	uint32_t headersize;    // offset of bitmaps in file
-	uint32_t flags;
-	uint32_t length;        // number of glyphs
-	uint32_t charsize;      // number of bytes for each character
-	uint32_t height, width; // max dimensions of glyphs
+struct font {
+    uint16_t height;
+    uint16_t width;
+    uint16_t charsize;
+    uint16_t count;
+    uint8_t *data;
 };
+
+int font_init(void *header, struct font *font);
+
+int font_draw(
+    struct font *f,
+    struct screen *s,
+    uint32_t glyph,
+    uint32_t color,
+    uint32_t x,
+    uint32_t y);

src/modules/main/main.c

@@ -1,6 +1,9 @@
 #include <stddef.h>
 #include <stdint.h>
 
+#include "font.h"
+#include "screen.h"
+
 void do_the_set_registers();
 
 #pragma pack(push, 1)
@@ -38,9 +41,33 @@ __attribute__((aligned(8)));
 void
 kernel_main(struct popcorn_data *header)
 {
-	uint32_t *p = header->frame_buffer;
-	uint32_t *end = p + (header->frame_buffer_size / sizeof(uint32_t));
-	while (p < end) *p++ = header->rmask;
+	struct screen screen;
+	struct font font;
+	int status = 0;
+
+	status = font_init(header->font, &font);
+
+	status = screen_init(
+		header->frame_buffer,
+		header->hres,
+		header->vres,
+		header->rmask,
+		header->gmask,
+		header->bmask,
+		&screen);
+
+	uint32_t color = header->gmask;
+	uint32_t perline = header->hres / font.width;
+	const char message[] = "Hello, I am text rendered by the kernel! :-D  ";
+	for (int i=0; i<sizeof(message); ++i) {
+		font_draw(
+			&font,
+			&screen,
+			message[i],
+			color,
+			(i % perline) * font.width + 10,
+			(i / perline) * font.height + 10);
+	}
 
 	do_the_set_registers(header);
 }

src/modules/main/screen.c

@@ -0,0 +1,42 @@
+#include "font.h"
+#include "screen.h"
+
+int
+screen_fill(struct screen *s, uint32_t color)
+{
+	const size_t len = s->hres * s->vres;
+	for (size_t i = 0; i < len; ++i)
+		s->data[i] = 0;
+	return 0;
+}
+
+int
+screen_init(
+	void *frame_buffer,
+	uint32_t hres,
+	uint32_t vres,
+	uint32_t rmask,
+	uint32_t gmask,
+	uint32_t bmask,
+	struct screen *s)
+{
+	s->data = frame_buffer;
+	s->hres = hres;
+	s->vres = vres;
+	s->rmask = rmask;
+	s->gmask = gmask;
+	s->bmask = bmask;
+
+	return screen_fill(s, 0);
+}
+
+int
+screen_pixel(
+	struct screen *s,
+	uint32_t x,
+	uint32_t y,
+	uint32_t color)
+{
+	s->data[x + y*s->hres] = color;
+	return 0;
+}

src/modules/main/screen.h

@@ -0,0 +1,30 @@
+#pragma once
+#include <stddef.h>
+#include <stdint.h>
+
+struct screen {
+	uint32_t *data;
+	uint32_t hres;
+	uint32_t vres;
+	uint32_t rmask;
+	uint32_t gmask;
+	uint32_t bmask;
+};
+
+int screen_init(
+	void *frame_buffer,
+	uint32_t hres,
+	uint32_t vres,
+	uint32_t rmask,
+	uint32_t gmask,
+	uint32_t bmask,
+	struct screen *s);
+
+int screen_fill(struct screen *s, uint32_t color);
+
+int screen_pixel(
+	struct screen *s,
+	uint32_t x,
+	uint32_t y,
+	uint32_t color);
+