Add some attribute handling for video module.

src/video.c

@@ -1,20 +1,63 @@
 #include "video.h"
 
+#include "io.h"
+
 #include <stdint.h>
 
 char *const VIDEO_MEMORY = (char *)0xd000;
 static uint16_t offset = 0;
+static bool hstretch = false;
+static bool vstretch = false;
 
-void video_putchar(char c) {
+void video_locate(uint8_t row, uint8_t column) {
-    if (c == '\n' || c == '\r') {
+    offset = (uint16_t)row * 80 + column;
-        offset += 80 - (offset % 80);
-
-    } else if (c == '\t') {
-        offset += 8 - offset % 8;
-    } else {
-        *(VIDEO_MEMORY + offset++) = c;
 }
 
+void video_enableHorizontalStretch(bool enable) {
+    hstretch = enable;
+}
+
+void video_enableVerticalStretch(bool enable) {
+    vstretch = enable;
+}
+
+void video_putchar(char c) {
+    // TODO(giomba): this function is not very consistent :sweat:
+    if (c == '\n' || c == '\r') {
+        offset += 80 - (offset % 80);
+        goto end;
+    }
+
+    if (hstretch) {
+        io_out(0x81, io_in(0x81) | 0x80);
+        *(VIDEO_MEMORY + offset) |= 0x08;
+        io_out(0x81, io_in(0x81) & ~0x80);
+    }
+
+    if (c == '\t') {
+        offset += 8 - offset % 8;
+        goto end;
+    }
+
+    *(VIDEO_MEMORY + offset) = c;
+
+    if (vstretch) {
+        *(VIDEO_MEMORY + offset + 80) = c;
+
+        io_out(0x81, io_in(0x81) | 0x80);
+        *(VIDEO_MEMORY + offset) |= 0x60;
+        *(VIDEO_MEMORY + offset + 80) |= 0x70;
+        if (hstretch)
+            *(VIDEO_MEMORY + offset + 80) |= 0x08;
+        io_out(0x81, io_in(0x81) & ~0x80);
+    }
+
+    ++offset;
+
+    if (hstretch)
+        ++offset;
+
+end:
     offset = offset % 2000;
 }
 

src/video.h

@@ -1,12 +1,16 @@
 #ifndef CEDA_PRINT_H
 #define CEDA_PRINT_H
 
+#include <stdbool.h>
 #include <stdint.h>
 
 extern char *const VIDEO_MEMORY;
 
 void video_cls(void);
 void video_put(uint8_t x, uint8_t y, char c);
+void video_locate(uint8_t row, uint8_t column);
+void video_enableHorizontalStretch(bool enable);
+void video_enableVerticalStretch(bool enable);
 void video_putchar(char c);
 
 #endif // CEDA_PRINT_H

src/video_a.asm

@@ -7,6 +7,7 @@ _video_cls:
     push    de
     push    hl
 
+    ; clear chars
     ld      hl,$d000
     ld      de,2000
     ld      c,$20
@@ -18,6 +19,28 @@ _video_cls_loop:
     or      e
     jp      nz,_video_cls_loop
 
+    ; enable attr video bank
+    in      a,($81)
+    or      a,$80
+    out     ($81),a
+
+    ; clear attributes
+    ld      hl,$d000
+    ld      de,2000
+    ld      c,$00
+_video_attr_cls_loop:
+    ld      (hl),c
+    inc     hl
+    dec     de
+    ld      a,d
+    or      e
+    jp      nz,_video_attr_cls_loop
+
+    ; restore char video bank
+    in      a,($81)
+    and     a,$7f
+    out     ($81),a
+
     pop     hl
     pop     de
     pop     bc