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https://github.com/V2RetroComputing/analog.git
synced 2024-12-01 08:52:01 +00:00
119 lines
3.5 KiB
C
119 lines
3.5 KiB
C
#include <pico/stdlib.h>
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#include "hires_color_patterns.h"
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#include "hires_dot_patterns.h"
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#include "vgabuf.h"
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#include "render.h"
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#include "vgaout.h"
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static void render_hires_line(uint line);
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static uint hires_line_to_mem_offset(uint line) {
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return ((line & 0x07) << 10) | ((line & 0x38) << 4) | (((line & 0xc0) >> 6) * 40);
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}
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void __time_critical_func(render_hires)() {
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vga_prepare_frame();
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render_border();
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for(uint line=0; line < 192; line++) {
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render_hires_line(line);
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}
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render_border();
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}
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void __time_critical_func(render_mixed_hires)() {
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vga_prepare_frame();
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render_border();
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for(uint line=0; line < 160; line++) {
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render_hires_line(line);
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}
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if(terminal_switches & TERMINAL_80COL) {
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for(uint line=20; line < 24; line++) {
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render_terminal_line(line);
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}
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} else {
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for(uint line=20; line < 24; line++) {
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render_text_line(line);
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}
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}
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render_border();
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}
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static void __time_critical_func(render_hires_line)(uint line) {
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struct vga_scanline *sl = vga_prepare_scanline();
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uint sl_pos = 0;
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const uint8_t *page = (const uint8_t *)((soft_switches & SOFTSW_PAGE_2) ? hgr_p2 : hgr_p1);
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const uint8_t *line_mem = page + hires_line_to_mem_offset(line);
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// Pad 40 pixels on the left to center horizontally
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while(sl_pos < 40/8) {
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sl->data[sl_pos] = (text_border|THEN_EXTEND_3) | ((text_border|THEN_EXTEND_3) << 16); // 8 pixels per word
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sl_pos++;
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}
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// Each hires byte contains 7 pixels which may be shifted right 1/2 a pixel. That is
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// represented here by 14 'dots' to precisely describe the half-pixel positioning.
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//
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// For each pixel, inspect a window of 8 dots around the pixel to determine the
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// precise dot locations and colors.
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//
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// Dots would be scanned out to the CRT from MSB to LSB (left to right here):
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//
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// previous | next
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// dots | dots
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// +-------------------+--------------------------------------------------+
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// dots: | 31 | 30 | 29 | 28 | 27 | 26 | 25 | 24 | 23 | ... | 14 | 13 | 12 | ...
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// | | | |
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// \______________|_________|______________/
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// | |
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// \_________/
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// current
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// pixel
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uint32_t dots = 0;
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uint oddness = 0;
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uint i;
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// Load in the first 14 dots
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dots |= (uint32_t)hires_dot_patterns[line_mem[0]] << 15;
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for(i=1; i < 41; i++) {
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// Load in the next 14 dots
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uint b = (i < 40) ? line_mem[i] : 0;
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if(b & 0x80) {
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// Extend the last bit from the previous byte
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dots |= (dots & (1u << 15)) >> 1;
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}
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dots |= (uint32_t)hires_dot_patterns[b] << 1;
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// Consume 14 dots
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for(uint j=0; j < 7; j++) {
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uint dot_pattern = oddness | ((dots >> 24) & 0xff);
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sl->data[sl_pos] = hires_color_patterns[dot_pattern];
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sl_pos++;
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dots <<= 2;
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oddness ^= 0x100;
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}
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}
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for(i=0; i < 40/8; i++) {
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sl->data[sl_pos] = (text_border|THEN_EXTEND_3) | ((text_border|THEN_EXTEND_3) << 16); // 8 pixels per word
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sl_pos++;
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}
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sl->length = sl_pos;
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sl->repeat_count = 1;
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vga_submit_scanline(sl);
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}
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