VGA print_string()

src/kernel/drivers/vga.c

@@ -1,6 +1,8 @@
 #include "vga.h"
 #include "../arch/i686/io.h"
 
+static uint8_t current_color = VGA_COLOR_BG_BLACK | VGA_COLOR_FG_WHITE;
+
 void set_char(int x, int y, char c){
     VGA_MEMORY[(x+y*VGA_WIDTH)*2] = c;
 }
@@ -23,3 +25,64 @@ int get_cursor(){
     offset += i686_inb(VGA_PORT_DATA); // Low byte
     return offset;
 }
+
+static int get_offset_y(int offset){
+    return offset / VGA_WIDTH;
+}
+
+static int get_offset_x(int offset){
+    return (offset - (get_offset_y(offset)*VGA_WIDTH));
+}
+
+int print_char(char c, int x, int y){
+    if(x >= VGA_WIDTH || y >= VGA_HEIGHT){ // Incorrect coords
+        VGA_MEMORY[2*VGA_WIDTH*VGA_HEIGHT-2] = 'E';
+        VGA_MEMORY[2*VGA_WIDTH*VGA_HEIGHT-1] = VGA_COLOR_BG_RED || VGA_COLOR_FG_BLACK;
+        return y*VGA_WIDTH+x;
+    }
+
+    int offset;
+    if(x >= 0 && y >= 0) offset = y*VGA_WIDTH+x;
+    else offset = get_cursor();
+
+    if(c == '\n'){
+        y = get_offset_y(offset);
+        offset = (y+1)*VGA_WIDTH;
+    }
+    else if(c == '\b'){
+        VGA_MEMORY[offset*2] = ' ';
+        VGA_MEMORY[offset*2+1] = current_color;
+    }
+    else{
+        VGA_MEMORY[offset*2] = c;
+        VGA_MEMORY[offset*2+1] = current_color;
+        offset++;
+    }
+
+    // TODO: Scroll
+    
+    set_cursor(offset);
+    return offset;
+}
+
+void print_string_at(char *str, int x, int y){
+    int offset;
+    if(x >= 0 && y >= 0){
+        offset = y*VGA_WIDTH+x;
+    }
+    else{
+        offset = get_cursor();
+        x = get_offset_x(offset);
+        y = get_offset_y(offset);
+    }
+
+    while(*str){
+        offset = print_char(*(str++), x, y);
+        x = get_offset_x(offset);
+        y = get_offset_y(offset);
+    }
+}
+
+void print_string(char *str){
+    print_string_at(str, -1, -1);
+}

src/kernel/drivers/vga.h

@@ -48,3 +48,6 @@ void set_char(int x, int y, char c);
 void set_color(int x, int y, uint8_t color);
 void set_cursor(int offset);
 int get_cursor();
+int print_char(char c, int x, int y);
+void print_string_at(char *str, int x, int y);
+void print_string(char *str);

src/kernel/main.c

@@ -2,9 +2,6 @@
 #include "drivers/vga.h"
 
 void __attribute__((cdecl)) kmain(uint64_t magic, uint64_t addr){
-    // Print a light cyan 'X' over green on the top left corner
-    set_char(0, 0, 'X');
-    set_color(0, 0, VGA_COLOR_BG_GREEN | VGA_COLOR_FG_LIGHT_CYAN);
-    set_cursor(1);
+    print_string("Hello world!\n:D");
     for(;;); // Halt here 
 }