New modular driver set for video

Started outlining how the modular driver set will look for video drawing routines. Currently supports Drawing pixels to the screen & Flushing backbuffer -> frontbuffer.
Still very much test code, tracer is used everywhere for debugging, NOT DEVELOP READY.
Many more draw routines need implementing - such as, but not limited to; drawRect, drawBitmap, drawLine, drawCurve, drawCircle.

TODO: Implement the aforementioned routines in all VESA modes + WindowManager.

src/driver/video/VESA.pas

@@ -13,19 +13,19 @@
 //  limitations under the License.
 
 { 
-	Driver->Video->VESA - Provides an interface the VESA drivers.
+	Driver->Video->VESA - VESA Display Driver.
 	
 	@author(Kieron Morris <kjm@kieronmorris.me>)
 }
-unit VESA;
+unit vesa;
 
 interface
 
 uses
-    Video, multiboot;
+    videotypes, tracer, multiboot, lmemorymanager;
-
-procedure init();
 
+//Init the driver, and register with the video interface in a state ready for execution.
+procedure init(Register : FRegisterDriver);
 
 implementation
 
@@ -38,51 +38,50 @@ var
     Block : uint32;
 
 begin
-    tracer.push_trace('vesa.allocateFrameBuffer.enter');
+    tracer.push_trace('VESA.allocateFrameBuffer.enter');
     LowerAddress:= ((Address) SHR 22)-1;
     UpperAddress:= ((Address + (Width * Height)) SHR 22)+1;
     For Block:=LowerAddress to UpperAddress do begin
         kpalloc(Block SHL 22);
     end;
-    tracer.push_trace('vesa.allocateFrameBuffer.enter');
+    tracer.push_trace('VESA.allocateFrameBuffer.exit');
 end;
 
 procedure initVESAFrameBuffer(VideoBuffer : PVideoBuffer; Location : uint64; Width : uint32; Height : uint32; BitsPerPixel : uint8);
 begin
-    if not(VideoBuffer^.MMIOBuffer.Initialized) then begin
+    tracer.push_trace('VESA.initVESAFrameBuffer.enter');
-        VideoBuffer^.MMIOBuffer.Location:= Location;
+    if not(VideoBuffer^.Initialized) then begin
-        VideoBuffer^.MMIOBuffer.BitsPerPixel:= BitsPerPixel;
+        VideoBuffer^.Location:= Location;
-        VideoBuffer^.MMIOBuffer.Width:= Width;
+        VideoBuffer^.BitsPerPixel:= BitsPerPixel;
-        VideoBuffer^.MMIOBuffer.Height:= Height;
+        VideoBuffer^.Width:= Width;
-        allocateVESAFrameBuffer(VideoBuffer^.MMIOBuffer.Location, VideoBuffer^.MMIOBuffer.Width, VideoBuffer^.MMIOBuffer.Height);
+        VideoBuffer^.Height:= Height;
-        VideoBuffer^.DefaultBuffer:= VideoBuffer^.MMIOBuffer.Location;
+        allocateVESAFrameBuffer(VideoBuffer^.Location, VideoBuffer^.Width, VideoBuffer^.Height);
-        VideoBuffer^.MMIOBuffer.Initialized:= True;
+        if VideoBuffer^.Location <> 0 then
+            VideoBuffer^.Initialized:= True;
     end;
+    tracer.push_trace('VESA.initVESAFrameBuffer.exit');
 end;
 
-procedure Flush(FrontBuffer : PVideoBuffer; BackBuffer : PVideoBuffer);
+function enable(VideoInterface : PVideoInterface) : boolean;
-var
-    x,y : uint32;
-    Back,Front : PuInt64;
-
 begin
-    if not(BackBuffer^.Initialized) then exit;
+    tracer.push_trace('VESA.enable.enter');
-    Back:= PUint64(BackBuffer^.Location);
+    initVESAFrameBuffer(@VideoInterface^.FrontBuffer, multiboot.multibootinfo^.framebuffer_addr, multiboot.multibootinfo^.framebuffer_width, multiboot.multibootinfo^.framebuffer_height, multiboot.multibootinfo^.framebuffer_bpp);
-    Front:= PuInt64(FrontBuffer^.Location);
+    case (VideoInterface^.FrontBuffer.BitsPerPixel) of
-    for x:=0 to (VideoDriver.MMIOBuffer.Width-1) div 2 do begin
+        08:VESA8.init(@VideoInterface^.DrawRoutines);
-        for y:=0 to (VideoDriver.MMIOBuffer.Height-1) div 2 do begin
+        16:VESA16.init(@VideoInterface^.DrawRoutines);
-            Front[(Y * VideoDriver.MMIOBuffer.Width)+X]:= Back[(Y * VideoDriver.MMIOBuffer.Width)+X];
+        24:VESA24.init(@VideoInterface^.DrawRoutines);
-        end;
+        32:VESA32.init(@VideoInterface^.DrawRoutines);
     end;
+    enable:= VideoInterface^.FrontBuffer.Initialized;  
+    tracer.push_trace('VESA.enable.exit');
 end;
 
-procedure init();
+procedure init(Register : FRegisterDriver);
 begin
-    initVESAFrameBuffer(@VideoDriver, multiboot.multibootinfo^.framebuffer_addr, multiboot.multibootinfo^.framebuffer_width, multiboot.multibootinfo^.framebuffer_height, multiboot.multibootinfo^.framebuffer_bpp); 
+    tracer.push_trace('VESA.init.enter');
-    VESA8.init();
+    if Register <> nil then
-    VESA16.init();
+        Register('VESA', @enable);   
-    VESA24.init();
+    tracer.push_trace('VESA.init.exit');
-    VESA32.init();
 end;
 
 end.

src/driver/video/VESA16.pas

@@ -13,18 +13,19 @@
 //  limitations under the License.
 
 { 
-	Driver->Video->VESA16 - Implementation of VESA 16bpp draw routines.
+	Driver->Video->VESA16 - Implementation of VESA 16bpp draw routines for the VESA Driver.
 	
 	@author(Kieron Morris <kjm@kieronmorris.me>)
 }
-unit VESA16;
+unit vesa16;
 
 interface
 
 uses
-    Video, VESA;
+    videotypes, vesa, tracer, color;
 
-procedure init();
+//Init the draw routines by providing what we support through the DrawRoutines struct.
+procedure init(DrawRoutines : PDrawRoutines);
 
 implementation
 
@@ -33,9 +34,10 @@ begin
 
 end;
 
-procedure init();
+procedure init(DrawRoutines : PDrawRoutines);
 begin
-    
+    tracer.push_trace('vesa16.init.enter');   
+    tracer.push_trace('vesa16.init.exit');
 end;
 
 end.

src/driver/video/VESA24.pas

@@ -13,18 +13,19 @@
 //  limitations under the License.
 
 { 
-	Driver->Video->VESA24 - Implementation of VESA 24bpp draw routines.
+	Driver->Video->VESA24 - Implementation of VESA 24bpp draw routines for the VESA Driver.
 	
 	@author(Kieron Morris <kjm@kieronmorris.me>)
 }
-unit VESA24;
+unit vesa24;
 
 interface
 
 uses
-    Video, VESA;
+    videotypes, vesa, tracer, color;
 
-procedure init();
+//Init the draw routines by providing what we support through the DrawRoutines struct.
+procedure init(DrawRoutines : PDrawRoutines);
 
 implementation
 
@@ -33,9 +34,10 @@ begin
 
 end;
 
-procedure init();
+procedure init(DrawRoutines : PDrawRoutines);
 begin
-    
+	tracer.push_trace('vesa24.init.enter');
+	tracer.push_trace('vesa24.init.exit');
 end;
 
 end.

src/driver/video/VESA32.pas

@@ -13,18 +13,19 @@
 //  limitations under the License.
 
 { 
-	Driver->Video->VESA32 - Implementation of VESA 32bpp draw routines.
+	Driver->Video->VESA32 - Implementation of VESA 32bpp draw routines for the VESA Driver.
 	
 	@author(Kieron Morris <kjm@kieronmorris.me>)
 }
-unit VESA32;
+unit vesa32;
 
 interface
 
 uses
-    Video, VESA;
+    videotypes, vesa, tracer, color;
 
-procedure init();
+//Init the draw routines by providing what we support through the DrawRoutines struct.
+procedure init(DrawRoutines : PDrawRoutines);
 
 implementation
 
@@ -34,14 +35,18 @@ var
     LocationIndex : Uint32;
 
 begin
+    tracer.push_trace('vesa32.DrawPixel.enter');
     Location:= Puint32(Buffer^.Location);
     LocationIndex:= (Y * Buffer^.Width) + X;
     Location[LocationIndex]:= uint32(Pixel);
+    tracer.push_trace('vesa32.DrawPixel.exit');
 end;
 
-procedure init();
+procedure init(DrawRoutines : PDrawRoutines);
 begin
-    
+    tracer.push_trace('vesa32.init.enter');
+    DrawRoutines^.DrawPixel:= @DrawPixel;
+    tracer.push_trace('vesa32.init.exit');
 end;
 
 end.

src/driver/video/VESA8.pas

@@ -13,18 +13,19 @@
 //  limitations under the License.
 
 { 
-	Driver->Video->VESA8 - Implementation of VESA 8bpp draw routines.
+	Driver->Video->VESA8 - Implementation of VESA 8bpp draw routines for the VESA Driver.
 	
 	@author(Kieron Morris <kjm@kieronmorris.me>)
 }
-unit VESA8;
+unit vesa8;
 
 interface
 
 uses
-    Video, VESA;
+    videotypes, vesa, tracer, color;
 
-procedure init();
+//Init the draw routines by providing what we support through the DrawRoutines struct.
+procedure init(DrawRoutines : PDrawRoutines);
 
 implementation
 
@@ -33,9 +34,10 @@ begin
 
 end;
 
-procedure init();
+procedure init(DrawRoutines : PDrawRoutines);
 begin
-    
+    tracer.push_trace('vesa8.init.enter');   
+    tracer.push_trace('vesa8.init.exit');  
 end;
 
 end.

src/driver/video/doublebuffer.pas

@@ -0,0 +1,94 @@
+//  Copyright 2021 Kieron Morris
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+
+{ 
+	Driver->Video->Doublebuffer - Implements a very basic double buffer, tested with VESA drivers.
+	
+	@author(Kieron Morris <kjm@kieronmorris.me>)
+}
+unit doublebuffer;
+
+interface
+
+uses
+    lmemorymanager, tracer, videotypes;
+
+//Init the driver, and register with the video interface in a state ready for execution.
+procedure init(Register : FRegisterDriver);
+
+implementation
+
+function allocateBackBuffer(Width : uint32; Height : uint32; BitsPerPixel : uint8) : uint64;
+begin
+    tracer.push_trace('doublebuffer.allocateBackBuffer.enter');
+    //This doesn't currently work... Needs a rework of lmemorymanager
+    allocateBackBuffer:= uint64(klalloc((Width * Height) * BitsPerPixel));
+    tracer.push_trace('doublebuffer.allocateBackBuffer.exit');
+end;
+
+procedure initBackBuffer(VInterface : PVideoInterface; Width : uint32; Height : uint32; BitsPerPixel : uint8);
+begin
+    tracer.push_trace('doublebuffer.initBackBuffer.enter');
+    if not(VInterface^.BackBuffer.Initialized) then begin
+        VInterface^.BackBuffer.Location:= allocateBackBuffer(Width, Height, BitsPerPixel);
+        if (VInterface^.BackBuffer.Location <> 0) then begin
+            VInterface^.BackBuffer.Width:= Width;
+            VInterface^.BackBuffer.Height:= Height;
+            VInterface^.BackBuffer.BitsPerPixel:= BitsPerPixel;
+            VInterface^.BackBuffer.Initialized:= True;
+        end;
+    end;
+    tracer.push_trace('doublebuffer.initBackBuffer.exit');
+end;
+
+procedure Flush(FrontBuffer : PVideoBuffer; BackBuffer : PVideoBuffer);
+var
+    X,Y : uint32;
+    Back,Front : PuInt64;
+
+begin
+    tracer.push_trace('doublebuffer.Flush.enter');
+    if not(BackBuffer^.Initialized) then exit;
+    if ((FrontBuffer^.Width > BackBuffer^.Width) or (FrontBuffer^.Height > BackBuffer^.Height)) then exit;
+    Back:= PUint64(BackBuffer^.Location);
+    Front:= PuInt64(FrontBuffer^.Location);
+    for X:=0 to (BackBuffer^.Width-1) div 2 do begin
+        for Y:=0 to (BackBuffer^.Height-1) div 2 do begin
+            Front[(Y * BackBuffer^.Width) + X]:= Back[(Y * BackBuffer^.Width) + X];
+        end;
+    end;
+    tracer.push_trace('doublebuffer.Flush.exit');
+end;
+
+function enable(VideoInterface : PVideoInterface) : boolean;
+begin
+    tracer.push_trace('doublebuffer.enable.enter');
+    enable:= false;
+    initBackBuffer(VideoInterface, VideoInterface^.FrontBuffer.Width, VideoInterface^.FrontBuffer.Height, VideoInterface^.FrontBuffer.BitsPerPixel);
+    if VideoInterface^.BackBuffer.Initialized then begin
+        VideoInterface^.DefaultBuffer:= @VideoInterface^.BackBuffer;
+        VideoInterface^.DrawRoutines.Flush:= @Flush;
+        enable:= true;
+    end;
+    tracer.push_trace('doublebuffer.enable.exit');
+end;
+
+procedure init(Register : FRegisterDriver);
+begin
+    tracer.push_trace('doublebuffer.init.enter');
+    Register('BASIC_DOUBLE_BUFFER', @enable);
+    tracer.push_trace('doublebuffer.init.exit');
+end;
+
+end.

src/driver/video/video.pas

@@ -13,7 +13,7 @@
 //  limitations under the License.
 
 { 
-	Driver->Video->Video - Provides abstract rasterization/drawing functions.
+	Driver->Video->Video - Provides an abstract rasterization/drawing interface.
 	
 	@author(Kieron Morris <kjm@kieronmorris.me>)
 }
@@ -22,83 +22,37 @@ unit video;
 interface
 
 uses
-    lmemorymanager, tracer, color, rand;
+    lmemorymanager, tracer, color, videotypes, hashmap;
 
 procedure init();
 procedure DrawPixel(X : uint32; Y : uint32; Pixel : TRGB32);
 procedure Flush();
-
+function register(DriverIdentifier : pchar; EnableCallback : FEnableDriver) : boolean;
-type
+function enable(DriverIdentifier : pchar) : boolean;
-    //Arbitrary pointer to a video buffer in memory
+function frontBufferWidth : uint32;
-    VideoBuffer = uint64;
+function frontBufferHeight : uint32;
-
+function frontBufferBpp : uint8;
-    //Struct representing a Memory Mapped Video Buffer
+function backBufferWidth : uint32;
-    TVideoBuffer = record
+function backBufferHeight : uint32;
-        //Has this buffer been initialized? Has it been paged/created in memory?
+function backBufferBpp : uint8;
-        Initialized     : Boolean;
-        //Location of the video buffer in memory as a QWORD.
-        Location        : VideoBuffer;
-        //How many bits per pixel?
-        BitsPerPixel    : uint8;
-        //Width of the buffer.
-        Width           : uint32;
-        //Height of the buffer.
-        Height          : uint32;
-    end;
-    //Pointer to a video buffer
-    PVideoBuffer = ^TVideoBuffer;
-
-    //Routines for drawing to the screen
-    TDrawRoutines = record
-        DrawPixel : FDrawPixel;
-        Flush     : FFlush;
-    end;
-    //Pointer to drawing routines
-    PDrawRoutines = ^TDrawRoutines;
-
-    //Struct representing the whole video driver.
-    TVideoDriver = record
-        //Default buffer to be used when rendering, front buffer for no double buffering, back buffer otherwise.
-        DefaultBuffer   : PVideoBuffer;
-        //Memory Mapped IO Buffer for raw rasterization.
-        MMIOBuffer      : TVideoBuffer;
-        //Back buffer used for double buffering, this is flushed to MMIOBuffer with flush();
-        BackBuffer      : TVideoBuffer;
-        //Drawing Routines
-        DrawRoutines    : TDrawRoutines;
-    end;
-    //Pointer to a video driver struct.
-    PVideoDriver = ^TVideoDriver;
-
-    //Draw a pixel to screenspace
-    FDrawPixel = procedure(Buffer : PVideoBuffer; X : uint32; Y : uint32; Pixel : TRGB32);
-    //Flush backbuffer to MMIO Buffer
-    FFlush     = procedure(FrontBuffer : PVideoBuffer; BackBuffer : PVideoBuffer);
 
 implementation
 
+Procedure dummyFDrawPixel(Buffer : PVideoBuffer; X : uint32; Y : uint32; Pixel : TRGB32);
+begin
+    tracer.push_trace('video.dummyFDrawPixel.enter');
+    //Do nothing
+end;
+
+Procedure dummyFFlush(FrontBuffer : PVideoBuffer; BackBuffer : PVideoBuffer);
+begin
+    tracer.push_trace('video.dummyFFlush.enter');
+    //Do nothing
+end;
+
 var
-    VideoDriver : TVideoDriver;
+    VideoInterface : TVideoInterface;
-
+    DriverMap      : PHashMap;
-function allocateBackBuffer(Width : uint32; Height : uint32; BitsPerPixel : uint8) : uint64;
-begin
-    Outputln('VIDEO','Start Kalloc Backbuffer');
-    //This doesn't currently work... Needs a rework of lmemorymanager
-    allocateBackBuffer:= uint64(klalloc((Width * Height) * BitsPerPixel));
-    Outputln('VIDEO','End Kalloc Backbuffer');
-end;
-
-procedure initBackBuffer(DriverInfo : PVideoDriver; Width : uint32; Height : uint32; BitsPerPixel : uint8);
-begin
-    if not(DriverInfo^.BackBuffer.Initialized) then begin
-        DriverInfo^.BackBuffer.Width:= Width;
-        DriverInfo^.BackBuffer.Height:= Height;
-        DriverInfo^.BackBuffer.BitsPerPixel:= BitsPerPixel;
-        DriverInfo^.BackBuffer.Location:= allocateBackBuffer(DriverInfo^.BackBuffer.Width, DriverInfo^.BackBuffer.Height, DriverInfo^.BackBuffer.BitsPerPixel);
-        DriverInfo^.DefaultBuffer:= DriverInfo^.BackBuffer.Location;
-        DriverInfo^.BackBuffer.Initialized:= True;
-    end;
-end;
 
 procedure init();
 var
@@ -107,23 +61,86 @@ var
 
 begin
     tracer.push_trace('video.init.enter');
-    
+    VideoInterface.FrontBuffer.Initialized:= false;
-    console.Outputln('VIDEO', 'Init VideoDriver MMIOBuffer');
+    VideoInterface.BackBuffer.Initialized:= false;
-       
+    VideoInterface.DefaultBuffer:= @VideoInterface.FrontBuffer;
-    console.Outputln('VIDEO', 'Init VideoDriver Backbuffer');
+    VideoInterface.DrawRoutines.DrawPixel:= @dummyFDrawPixel;
-    //initBackBuffer(@VideoDriver, multiboot.multibootinfo^.framebuffer_width, multiboot.multibootinfo^.framebuffer_height, multiboot.multibootinfo^.framebuffer_bpp);
+    VideoInterface.DrawRoutines.Flush:= @dummyFFlush;
-
+    DriverMap:= hashmap.new;
     tracer.push_trace('video.init.exit');
 end;
 
+function register(DriverIdentifier : pchar; EnableCallback : FEnableDriver) : boolean;
+var
+    Value : Void;
+
+begin
+    tracer.push_trace('video.register.enter');
+    register:= false;
+    Value:= Hashmap.get(DriverMap, DriverIdentifier);
+    if (Value = nil) then begin
+        Hashmap.add(DriverMap, DriverIdentifier, void(EnableCallback));
+        register:= true;
+    end;
+    tracer.push_trace('video.register.exit');
+end;
+
+function enable(DriverIdentifier : pchar) : boolean;
+var
+    Value : Void;
+
+begin
+    tracer.push_trace('video.enable.enter');
+    enable:= false;
+    Value:= Hashmap.get(DriverMap, DriverIdentifier);
+    if (Value <> nil) then begin
+        enable:= FEnableDriver(Value)(@VideoInterface);
+    end;
+    tracer.push_trace('video.enable.exit');
+end;
+
 procedure DrawPixel(X : uint32; Y : uint32; Pixel : TRGB32);
 begin
-
+    tracer.push_trace('video.DrawPixel.enter');
+    VideoInterface.DrawRoutines.DrawPixel(VideoInterface.DefaultBuffer, X, Y, Pixel);
+    tracer.push_trace('video.DrawPixel.exit');
 end;
 
 procedure Flush();
 begin
+    tracer.push_trace('video.Flush.enter');
+    VideoInterface.DrawRoutines.Flush(@VideoInterface.FrontBuffer, @VideoInterface.BackBuffer);
+    tracer.push_trace('video.Flush.exit');
+end;
 
+function frontBufferWidth : uint32;
+begin
+    frontBufferWidth:= VideoInterface.FrontBuffer.Width;
+end;
+
+function frontBufferHeight : uint32;
+begin
+    frontBufferHeight:= VideoInterface.FrontBuffer.Height;
+end;
+
+function frontBufferBpp : uint8;
+begin
+    frontBufferBpp:= VideoInterface.FrontBuffer.BitsPerPixel;
+end;
+
+function backBufferWidth : uint32;
+begin
+    backBufferWidth:= VideoInterface.BackBuffer.Width;
+end;
+
+function backBufferHeight : uint32;
+begin
+    backBufferHeight:= VideoInterface.BackBuffer.Height;
+end;
+
+function backBufferBpp : uint8;
+begin
+    backBufferBpp:= VideoInterface.BackBuffer.BitsPerPixel;
 end;
 
 end.

src/driver/video/videotypes.pas

@@ -0,0 +1,83 @@
+//  Copyright 2021 Kieron Morris
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+
+{ 
+	Driver->Video->Videotypes - Provides types relating to the video framework & driver interface.
+	
+	@author(Kieron Morris <kjm@kieronmorris.me>)
+}
+unit videotypes;
+
+interface
+
+uses
+    color;
+
+type
+    //Arbitrary pointer to a video buffer in memory
+    VideoBuffer = uint32;
+
+    //Struct representing a Memory Mapped Video Buffer
+    TVideoBuffer = record
+        //Has this buffer been initialized? Has it been paged/created in memory?
+        Initialized     : Boolean;
+        //Location of the video buffer in memory as a QWORD.
+        Location        : VideoBuffer;
+        //How many bits per pixel?
+        BitsPerPixel    : uint8;
+        //Width of the buffer.
+        Width           : uint32;
+        //Height of the buffer.
+        Height          : uint32;
+    end;
+    //Pointer to a video buffer
+    PVideoBuffer = ^TVideoBuffer;
+
+    //(Abstract) Draw a pixel to screenspace
+    FDrawPixel = procedure(Buffer : PVideoBuffer; X : uint32; Y : uint32; Pixel : TRGB32);
+    //(Abstract) Flush backbuffer to MMIO Buffer
+    FFlush     = procedure(FrontBuffer : PVideoBuffer; BackBuffer : PVideoBuffer);
+
+    //Routines for drawing to the screen
+    TDrawRoutines = record
+        DrawPixel : FDrawPixel;
+        Flush     : FFlush;
+    end;
+    //Pointer to drawing routines
+    PDrawRoutines = ^TDrawRoutines;
+
+    //Struct representing the whole video driver.
+    TVideoInterface = record
+        //Default buffer to be used when rendering, front buffer for no double buffering, back buffer otherwise.
+        DefaultBuffer   : PVideoBuffer;
+        //Memory Mapped IO Buffer for raw rasterization.
+        FrontBuffer     : TVideoBuffer;
+        //Back buffer used for double buffering, this is flushed to FrontBuffer with flush();
+        BackBuffer      : TVideoBuffer;
+        //Drawing Routines
+        DrawRoutines    : TDrawRoutines;
+    end;
+    //Pointer to a video interface struct.
+    PVideoInterface = ^TVideoInterface;
+
+    //(Abstract) Enable method for a driver, called from video to enable driver.
+    FEnableDriver = function(VideoInterface : PVideoInterface) : boolean;
+    //(Abstract) Register driver, called from a driver to register with the video interface.
+    FRegisterDriver = function(DriverIdentifier : pchar; EnableCallback : FEnableDriver) : boolean;
+    //(Abstract) Init driver, called from _somewhere_ to start the driver and register it with the video interface.
+    FInitDriver = procedure(Register : FRegisterDriver);
+
+implementation
+
+end.

src/include/color.pas

@@ -1,3 +1,22 @@
+//  Copyright 2021 Kieron Morris
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+
+{ 
+	Include->Color - Provides types relating to color/graphics.
+	
+	@author(Kieron Morris <kjm@kieronmorris.me>)
+}
 unit color;
 
 interface
@@ -31,6 +50,9 @@ type
 const
     black : TRGB32 = (B: 000; G: 000; R: 000; A: 000);
     white : TRGB32 = (B: 255; G: 255; R: 255; A: 000);
+    red   : TRGB32 = (B: 000; G: 000; R: 255; A: 000);
+    green : TRGB32 = (B: 000; G: 255; R: 000; A: 000);
+    blue  : TRGB32 = (B: 255; G: 000; R: 000; A: 000);
 
 implementation
 

src/kernel.pas

@@ -54,7 +54,8 @@ uses
      base64,
      rand,
      terminal,
-     hashmap, vfs, video;
+     hashmap, vfs, 
+     video, vesa, doublebuffer, color;
  
 procedure kmain(mbinfo: Pmultiboot_info_t; mbmagic: uint32); stdcall;
  
@@ -124,6 +125,8 @@ var
 
    HM              : PHashMap;
 
+   colour          : TRGB32;
+   
 begin
      { Init the base system unit }
      System.init();
@@ -204,6 +207,27 @@ begin
      tracer.init();
 
      video.init();
+     vesa.init(@video.register);
+     doublebuffer.init(@video.register);
+     video.enable('VESA');
+     video.enable('BASIC_DOUBLE_BUFFER');
+     colour:= color.red;
+     while true do begin
+        for i:=0 to video.frontBufferWidth-1 do begin
+            for z:=0 to video.frontBufferHeight-1 do begin
+                video.DrawPixel(i, z, colour);
+            end;
+        end;
+        
+        if uint32(colour) = uint32(color.red) then
+            colour:= color.green
+        else if uint32(colour) = uint32(color.green) then
+            colour:= color.blue
+        else if uint32(colour) = uint32(color.blue) then
+            colour:= color.red;
+
+        video.Flush();
+     end;
 
      { VFS Init }
      vfs.init();