From 21491514b3642a321ce65f2a07428f63c4d9feb5 Mon Sep 17 00:00:00 2001
From: Benji Dial <Benji3.141@gmail.com>
Date: Sun, 8 Nov 2020 11:11:49 -0500
Subject: manual viewer, "swap colors" system call

---
 src/kernel/idt.c    | 3 ++-
 src/kernel/isrs.asm | 2 +-
 src/kernel/vga.c    | 5 +++++
 src/kernel/vga.h    | 1 +
 4 files changed, 9 insertions(+), 2 deletions(-)

(limited to 'src/kernel')

diff --git a/src/kernel/idt.c b/src/kernel/idt.c
index 1b8e548..ebeea17 100644
--- a/src/kernel/idt.c
+++ b/src/kernel/idt.c
@@ -120,7 +120,8 @@ void const *syscall_table[] = {
   &vga_print_at,
   &sc_count_of_dir,
   &vga_blank,
-  &vga_set_color
+  &vga_set_color,
+  &vga_swap_color
 };
 
 //these aren't really void ()'s, but gcc complains if we take an address of a void, so we give it a type
diff --git a/src/kernel/isrs.asm b/src/kernel/isrs.asm
index e7573ae..472bb40 100644
--- a/src/kernel/isrs.asm
+++ b/src/kernel/isrs.asm
@@ -23,7 +23,7 @@ extern on_kbd_isr
 extern make_sure_tasks
 extern exception_halt
 
-n_syscalls equ 0xf
+n_syscalls equ 0x10
 
 ;section .bss
 ;_debug_is_start_task resb 1
diff --git a/src/kernel/vga.c b/src/kernel/vga.c
index 42da312..6ae1588 100644
--- a/src/kernel/vga.c
+++ b/src/kernel/vga.c
@@ -12,6 +12,11 @@ void vga_set_color(uint8_t new_color) {
   mask = new_color << 8;
 }
 
+void vga_swap_color(uint16_t pos) {
+  uint8_t *color_byte = (uint8_t *)(VGA_START + (pos >> 8) * VGA_COLUMNS + (pos & 0xff)) + 1;
+  *color_byte = (*color_byte << 4) + (*color_byte >> 4);
+}
+
 static void vga_scroll() {
   for (uint32_t *i = (uint32_t *)VGA_START; i < (uint32_t *)(VGA_END - VGA_COLUMNS); ++i)
     *i = *(i + VGA_COLUMNS / 2);
diff --git a/src/kernel/vga.h b/src/kernel/vga.h
index fa97e11..dd1c906 100644
--- a/src/kernel/vga.h
+++ b/src/kernel/vga.h
@@ -7,5 +7,6 @@ void vga_print_at(uint16_t pos, const char *sz);
 void vga_set_color(uint8_t color);
 void vga_blank();
 void vga_printch(char ch);
+void vga_swap_color(uint16_t pos);
 
 #endif
\ No newline at end of file
-- 
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