[Minios-devel] [UNIKRAFT PATCH 1/2] plat/kvm: Implement scrolling for VGA text mode

[Florian Schmidt <florian.schmidt@xxxxxxxxx>]

So far, when the text output overflowed the bottom of the console, it
was completely cleared, and output started from the top again. This
implement a scrolling functionality when we hit the bottom of the
console.

Signed-off-by: Florian Schmidt <florian.schmidt@xxxxxxxxx>
---
 plat/kvm/x86/vga_console.c | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/plat/kvm/x86/vga_console.c b/plat/kvm/x86/vga_console.c
index 4746dd7..a1b5cf7 100644
--- a/plat/kvm/x86/vga_console.c
+++ b/plat/kvm/x86/vga_console.c
@@ -28,6 +28,7 @@
 
 #include <sys/types.h>
 #include <stdint.h>
+#include <string.h>
 #include <kvm-x86/vga_console.h>
 
 /* Hardware text mode color constants. */
@@ -95,6 +96,26 @@ static void terminal_putentryat(char c, uint8_t color, 
size_t x, size_t y)
 
        terminal_buffer[index] = vga_entry(c, color);
 }
+static void vga_scroll(void)
+{
+       size_t i;
+
+       for (i = 1; i < VGA_HEIGHT; i++) {
+               memcpy(terminal_buffer + ((i - 1) * VGA_WIDTH),
+                       terminal_buffer + (i * VGA_WIDTH), VGA_WIDTH * 2);
+       }
+       for (i = 0; i < VGA_WIDTH; i++)
+               terminal_buffer[((VGA_HEIGHT - 1) * VGA_WIDTH) + i]
+                       = vga_entry(' ', terminal_color);
+}
+
+static void vga_newline(void)
+{
+       if (terminal_row == VGA_HEIGHT - 1)
+               vga_scroll();
+       else
+               terminal_row++;
+}
 
 void _libkvmplat_vga_putc(char c)
 {
@@ -114,8 +135,7 @@ void _libkvmplat_vga_putc(char c)
                break;
        case '\n':
                _libkvmplat_vga_putc('\r');
-               if (++terminal_row == VGA_HEIGHT)
-                       terminal_row = 0;
+               vga_newline();
                break;
        case '\r':
                terminal_column = 0;
@@ -128,8 +148,7 @@ void _libkvmplat_vga_putc(char c)
 
                if (terminal_column == VGA_WIDTH) {
                        terminal_column = 0;
-                       if (++terminal_row == VGA_HEIGHT)
-                               terminal_row = 0;
+                       vga_newline();
                }
                break;
        default:
@@ -137,8 +156,7 @@ void _libkvmplat_vga_putc(char c)
                                terminal_column, terminal_row);
                if (++terminal_column == VGA_WIDTH) {
                        terminal_column = 0;
-                       if (++terminal_row == VGA_HEIGHT)
-                               terminal_row = 0;
+                       vga_newline();
                }
                break;
        }
-- 
2.18.0


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