File Selector uses a very simple double buffer

helper.c

@@ -1,8 +1,8 @@
 #include "helper.h"
 
-uint16_t *nextLine(uint16_t *p) {
+uint16_t *nextLine(uint16_t *p, uint16_t *b) {
     uintptr_t v = (uintptr_t)p;
-    return (uint16_t *)(v + (160 - ((v - 0xb8000) % 160)));
+    return (uint16_t *)(v + (160 - ((v - (uintptr_t)b) % 160)));
 }
 
 void V8086Int(uint8_t interrupt, union V86Regs_t *regs) {

helper.h

@@ -11,7 +11,7 @@ void SetVideo25Lines();
 void SetVideo50Lines();
 void SetCursorDisabled();
 
-uint16_t *nextLine(uint16_t *p);
+uint16_t *nextLine(uint16_t *p, uint16_t *b);
 
 uint32_t OpenVol(VOLINFO *vi);
 uint32_t OpenDir(uint8_t *path, VOLINFO *vi, DIRINFO *di);

hexedit.c

@@ -283,7 +283,7 @@ void HexEditor(uint8_t *path, VOLINFO *vi) {
                     else vga_text += printChar(' ', vga_text);
                 }
                 vga_text += printChar('|', vga_text);
-                vga_text = nextLine(vga_text);
+                vga_text = nextLine(vga_text,(uint16_t*)0xb8000);
             }
             // Clear remainder of screen
             for (;vga_text < &((uint16_t*)0xb8000)[screenSize]; vga_text++)

kernel.c

@@ -202,8 +202,8 @@ Protected Only (1MB+)
 400000 - 700000 Usermode Code (3mB)
 700000 - 800000 Usermode Stack (1mB)
 */
-void DrawScreen() {
-    uint16_t *vga_text = (uint16_t *)0xB8000;
+void DrawScreen(uint16_t *vga) {
+    uint16_t *vga_text = vga;
     // clear screen
     for (int i = 0; i < 80*25; i++)
         vga_text[i] = 0x1f00;
@@ -255,8 +255,8 @@ void RestoreVGA() {
 
 int32_t fileCount;
 DIRENT *entries = (DIRENT*)0x400000;
-void PrintFileList() {
-    uint16_t *vga_text = &((uint16_t *)0xb8000)[80*6+3];
+void PrintFileList(uint16_t *vga) {
+    uint16_t *vga_text = &((uint16_t *)vga)[80*6+3];
     for (int i = 0; i < fileCount; i++) {
         DIRENT *de = &entries[i];
         for (int i = 0; i < 11 && de->name[i]; i++) {
@@ -270,7 +270,7 @@ void PrintFileList() {
                 ((uint32_t)de->filesize_2 << 16) +
                 ((uint32_t)de->filesize_3 << 24), vga_text);
         *(uint8_t*)vga_text++ = 'B';
-        vga_text = nextLine(vga_text) + 3;
+        vga_text = nextLine(vga_text, vga) + 3;
     }
 }
 char IsDir(DIRENT *de) {
@@ -287,6 +287,7 @@ void ScancodeTest() {
     }
 }
 extern void create_child(uint32_t esp, uint32_t eip, uint32_t argc, ...);
+uint16_t FileSelectScreen[80*25];
 void FileSelect() {
     uint8_t current_path[80];
     uintptr_t current_path_end;
@@ -295,10 +296,10 @@ void FileSelect() {
     current_path[0] = '/';
     current_path_end = 1;
     fileCount = 5;
-    uint16_t *vga_text = (uint16_t *)0xb8000;
+    uint16_t *vga_text = (uint16_t *)FileSelectScreen;
     int32_t fileHovered = 0, lastFileHovered = 0;
     for (char reload = 1;;) {
-        DrawScreen();
+        DrawScreen(vga_text);
         // Info line (4)
         {
             uint16_t *vga = &vga_text[80*4 + 79 - 24];
@@ -323,12 +324,15 @@ void FileSelect() {
             GetFileList(entries, &fileCount, &vi, &di);
             reload = 0;
         }
-        PrintFileList();
+        PrintFileList(vga_text);
         if (lastFileHovered != fileHovered) {
             *(uint8_t*)&vga_text[80*(6+lastFileHovered)+2] = ' ';
             lastFileHovered = fileHovered;
         }
         *(uint8_t*)&vga_text[80*(6+fileHovered)+2] = '>';
+        // Copy to real VGA
+        for (int i = 0; i < 80*25; i++)
+            ((uint16_t*)0xb8000)[i] = vga_text[i];
         uint16_t key = get_scancode();
         uint8_t path[13];
         switch (key & 0xff) { // scancode component
@@ -476,7 +480,7 @@ void start() {
     //if (key == 't' || key == 'T')
     //    create_child(GetFreeStack(), (uintptr_t)RunTests, 0);
     RestoreVGA();
-    DrawScreen();
+    DrawScreen((uint16_t*)0xb8000);
     uint32_t stack;
     asm volatile("mov %%esp,%%eax":"=a"(stack));
     stack = ((stack - 0x4000) / 0x1000) * 0x1000;
@@ -490,7 +494,7 @@ void start() {
             enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry), &regs);
         }
         RestoreVGA();
-        DrawScreen();
+        DrawScreen((uint16_t*)0xb8000);
         vga_text = &((word*)0xb8000)[80*4 + 2];
         vga_text += printStr("Error loading file select. Ensure the disk has a valid MBR and FAT partition.", vga_text);
         vga_text = &((word*)0xb8000)[80*5 + 2];

progs.c

@@ -87,7 +87,7 @@ void TextViewTest(uint8_t *path, VOLINFO *vi) {
             for (; o < (int32_t)fileLen && vga_text < &((uint16_t*)0xb8000)[screenSize]; c = diskReadBuf[++o]) {
                 // newline
                 if (c == 0x0A) {
-                    vga_text = nextLine(vga_text);
+                    vga_text = nextLine(vga_text,(uint16_t*)0xb8000);
                     line++;
                     {
                         uint16_t *vga_tmp = vga_text;
@@ -225,7 +225,7 @@ void ProgramLoadTest(uint8_t *path, VOLINFO *vi) {
     vga_text += printStr("\", ", vga_text);
     vga_text += printDec(successcount, vga_text);
     vga_text += printStr(" Bytes.", vga_text);
-    vga_text = nextLine(vga_text);
+    vga_text = nextLine(vga_text,(uint16_t*)0xb8000);
     vga_text += printStr("Press any key to run.", vga_text);
     kbd_wait();
     uint32_t res = create_user_child(0x800000, 0x400000, 0);