changed video mode management, moved to video driver,

the VGA driver registers his specific mode data with the
video driver
kernel function now use virtual functions of the video driver

7 files changed, 223 insertions, 161 deletions

diff --git a/src/drivers/video/vga.c b/src/drivers/video/vga.c
index 094a117..c38bee1 100644
--- a/src/drivers/video/vga.c
+++ b/src/drivers/video/vga.c
@@ -11,10 +11,83 @@
 
 static vga_vtable_t const vga_vtable = {
 	{
-	vga_activate,
-	vga_deactivate,
-	vga_deinit,
-	vga_print_info
+		{
+			vga_activate,
+			vga_deactivate,
+			vga_deinit,
+			vga_print_info
+		},
+		video_register_mode,
+		video_supports_mode,
+		video_set_mode,
+		vga_switch_mode
+	}
+};
+
+// from http://files.osdev.org/mirrors/geezer/osd/graphics/modes.c
+static vga_mode_t modes[] = {
+	{ { VIDEO_MODE_TYPE_TEXT, 640, 480, 4 },
+		{ 
+		/* MISC */
+			0x67,
+		/* SEQ */
+			0x03, 0x00, 0x03, 0x00, 0x02,
+		/* CRTC */
+			0x5F, 0x4F, 0x50, 0x82, 0x55, 0x81, 0xBF, 0x1F,
+			0x00, 0x4F, 0x0D, 0x0E, 0x00, 0x00, 0x00, 0x50,
+			0x9C, 0x0E, 0x8F, 0x28, 0x1F, 0x96, 0xB9, 0xA3,
+			0xFF,
+		/* GC */
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x10, 0x0E, 0x00,
+			0xFF,
+		/* AC */
+			0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x14, 0x07,
+			0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x3E, 0x3F,
+			0x0C, 0x00, 0x0F, 0x08, 0x00
+		},
+		NULL
+	},
+	{ { VIDEO_MODE_TYPE_GRAPHICS, 320, 200, 8 },
+		{
+		/* MISC */
+			0x63,
+		/* SEQ */
+			0x03, 0x01, 0x0F, 0x00, 0x0E,
+		/* CRTC */
+			0x5F, 0x4F, 0x50, 0x82, 0x54, 0x80, 0xBF, 0x1F,
+			0x00, 0x41, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0x9C, 0x0E, 0x8F, 0x28, 0x40, 0x96, 0xB9, 0xA3,
+			0xFF,
+		/* GC */
+			0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x05, 0x0F,
+			0xFF,
+		/* AC */
+			0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+			0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
+			0x41, 0x00, 0x0F, 0x00, 0x00
+		},
+		NULL
+	},
+	{ { VIDEO_MODE_TYPE_GRAPHICS, 640, 480, 4 },
+		{
+		/* MISC */
+			0xE3,
+		/* SEQ */
+			0x03, 0x01, 0x08, 0x00, 0x06,
+		/* CRTC */
+			0x5F, 0x4F, 0x50, 0x82, 0x54, 0x80, 0x0B, 0x3E,
+			0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+			0xEA, 0x0C, 0xDF, 0x28, 0x00, 0xE7, 0x04, 0xE3,
+			0xFF,
+		/* GC */
+			0x00, 0x00, 0x00, 0x00, 0x03, 0x00, 0x05, 0x0F,
+			0xFF,
+		/* AC */
+			0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x14, 0x07,
+			0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x3E, 0x3F,
+			0x01, 0x00, 0x0F, 0x00, 0x00
+		},
+		NULL
 	}
 };
 
@@ -22,7 +95,7 @@ void vga_init( vga_t *vga, interrupt_t *interrupt, void *context )
 {
 	memset( vga, 0, sizeof( vga_t ) );
 	
-	driver_init( (driver_t *)vga, DRIVER_TYPE_VIDEO, interrupt, context );
+	video_init( (video_t *)vga, interrupt, context );
 
 	port8_init( &vga->misc_port, 0x3C2 );
 	port8_init( &vga->crtc_index_port, 0x3D4 );
@@ -37,6 +110,11 @@ void vga_init( vga_t *vga, interrupt_t *interrupt, void *context )
 	port8_init( &vga->attribute_controller_reset_port, 0x3DA );
 
 	((driver_t *)vga)->vtable = (driver_vtable_t *)&vga_vtable;
+
+	// register modes
+	for( int i = 0; modes[i].base.x != 0; i++ ) {
+		((video_vtable_t *)(vga->base.base.vtable))->register_mode( vga, (const video_mode_t *)&modes[i] );
+	}
 }
 
 void vga_activate( void *obj )
@@ -106,113 +184,7 @@ static void write_registers( vga_t *vga, uint8_t *regs )
 	(void)port8_read( &vga->attribute_controller_reset_port );
 	port8_write( &vga->attribute_controller_index_port, 0x20 );
 }
-
-vga_mode_t vga_make_mode( const vga_mode_type_t mode_type, const int x, const int y, const int color_depth )
-{
-	vga_mode_t mode;
-
-	mode.mode_type = mode_type;
-	mode.x = x;
-	mode.y = y;
-	mode.color_depth = color_depth;
-
-	return mode;
-}
 	
-// from http://files.osdev.org/mirrors/geezer/osd/graphics/modes.c
-static vga_mode_t modes[] = {
-	{ VGA_MODE_TYPE_TEXT, 640, 480, 4,
-		{ 
-		/* MISC */
-			0x67,
-		/* SEQ */
-			0x03, 0x00, 0x03, 0x00, 0x02,
-		/* CRTC */
-			0x5F, 0x4F, 0x50, 0x82, 0x55, 0x81, 0xBF, 0x1F,
-			0x00, 0x4F, 0x0D, 0x0E, 0x00, 0x00, 0x00, 0x50,
-			0x9C, 0x0E, 0x8F, 0x28, 0x1F, 0x96, 0xB9, 0xA3,
-			0xFF,
-		/* GC */
-			0x00, 0x00, 0x00, 0x00, 0x00, 0x10, 0x0E, 0x00,
-			0xFF,
-		/* AC */
-			0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x14, 0x07,
-			0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x3E, 0x3F,
-			0x0C, 0x00, 0x0F, 0x08, 0x00
-		},
-		NULL
-	},
-	{ VGA_MODE_TYPE_GRAPHICS, 320, 200, 8,
-		{
-		/* MISC */
-			0x63,
-		/* SEQ */
-			0x03, 0x01, 0x0F, 0x00, 0x0E,
-		/* CRTC */
-			0x5F, 0x4F, 0x50, 0x82, 0x54, 0x80, 0xBF, 0x1F,
-			0x00, 0x41, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-			0x9C, 0x0E, 0x8F, 0x28, 0x40, 0x96, 0xB9, 0xA3,
-			0xFF,
-		/* GC */
-			0x00, 0x00, 0x00, 0x00, 0x00, 0x40, 0x05, 0x0F,
-			0xFF,
-		/* AC */
-			0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
-			0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F,
-			0x41, 0x00, 0x0F, 0x00, 0x00
-		},
-		NULL
-	},
-	{ VGA_MODE_TYPE_GRAPHICS, 640, 480, 4,
-		{
-		/* MISC */
-			0xE3,
-		/* SEQ */
-			0x03, 0x01, 0x08, 0x00, 0x06,
-		/* CRTC */
-			0x5F, 0x4F, 0x50, 0x82, 0x54, 0x80, 0x0B, 0x3E,
-			0x00, 0x40, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-			0xEA, 0x0C, 0xDF, 0x28, 0x00, 0xE7, 0x04, 0xE3,
-			0xFF,
-		/* GC */
-			0x00, 0x00, 0x00, 0x00, 0x03, 0x00, 0x05, 0x0F,
-			0xFF,
-		/* AC */
-			0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x14, 0x07,
-			0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x3E, 0x3F,
-			0x01, 0x00, 0x0F, 0x00, 0x00
-		},
-		NULL
-	}
-};
-
-bool vga_supports_mode( const vga_mode_t mode )
-{
-	for( int i = 0; modes[i].x != 0; i++ ) {
-		if( 	mode.mode_type == modes[i].mode_type &&
-			mode.x == modes[i].x &&
-			mode.y == modes[i].y &&
-			mode.color_depth == modes[i].color_depth ) {
-			return true;
-		}
-	}
-
-	return false;
-}
-
-static int get_matching_mode_idx( const vga_mode_t mode )
-{
-	for( int i = 0; modes[i].x != 0; i++ ) {
-		if( 	mode.mode_type == modes[i].mode_type &&
-			mode.x == modes[i].x &&
-			mode.y == modes[i].y &&
-			mode.color_depth == modes[i].color_depth ) {
-			return i;
-		}
-	}
-
-	return -1;
-}
 
 static uint8_t *get_frame_buffer_segment( vga_t *vga )
 {
@@ -273,27 +245,22 @@ static size_t get_frame_buffer_segment_size( vga_t *vga )
 	return segment_size;
 }
 
-bool vga_set_mode( vga_t *vga, const vga_mode_t mode )
+bool vga_switch_mode( void *obj, const video_mode_t *mode )
 {
-	// do not allow unknown timings!
-	if( !vga_supports_mode( mode ) ) {
-		return false;
-	}
-
-	vga_mode_t matching_mode = modes[get_matching_mode_idx( mode )];
+	vga_t *vga = (vga_t *)obj;
+	vga_mode_t *vga_mode = (vga_mode_t *)mode;
 
-	write_registers( vga, matching_mode.regs );
+	write_registers( vga, vga_mode->regs );
 
-	vga->mode = mode;
-	vga->mode.segment = get_frame_buffer_segment( vga );
-	vga->mode.segment_size = get_frame_buffer_segment_size( vga );
+	vga->mode = (vga_mode_t *)mode;
+	vga->mode->segment = get_frame_buffer_segment( vga );
+	vga->mode->segment_size = get_frame_buffer_segment_size( vga );
 
 	vga_use_z_buffer( vga, false );
 
 	return true;
 }
 
-
 vga_color_t vga_make_RGB( int R, int G, int B )
 {
 	vga_color_t c;
@@ -336,7 +303,7 @@ static uint8_t get_color_index( const vga_color_t c )
 
 static bool params_ok( vga_t *vga, const int x, const int y )
 {
-	if( x < 0 || x > vga->mode.x || y < 0 || y > vga->mode.y ) {
+	if( x < 0 || x > vga->mode->base.x || y < 0 || y > vga->mode->base.y ) {
 		return false;
 	}
 
@@ -347,12 +314,12 @@ void vga_set_pixel( vga_t *vga, const int x, const int y, const vga_color_t colo
 {
 	if( !params_ok( vga, x, y ) ) {
 		kernel_panic( "Pixel coordinates are out of bounds: (%d, %d), resolution is only (%d, %d)",
-			x, y, vga->mode.x, vga->mode.y );
+			x, y, vga->mode->base.x, vga->mode->base.y );
 	}
 
 	uint8_t color_idx = get_color_index( color );
 
-	uint8_t *addr = vga->base_addr + vga->mode.x * y + x;
+	uint8_t *addr = vga->base_addr + vga->mode->base.x * y + x;
 
 	*addr = color_idx;
 }	
@@ -361,18 +328,18 @@ void vga_draw_rectangle( vga_t *vga, const int x, const int y, const int w, cons
 {
 	if( !params_ok( vga, x, y ) ) {
 		kernel_panic( "Rectangle start coordinates are out of bounds: (%d, %d), resolution is only (%d, %d)",
-			x, y, vga->mode.x, vga->mode.y );
+			x, y, vga->mode->base.x, vga->mode->base.y );
 	}
 
 	if( !params_ok( vga, x + w, y + h ) ) {
 		kernel_panic( "Rectangle end coordinates are out of bounds: (%d, %d), resolution is only (%d, %d)",
-			x + w, y + h, vga->mode.x, vga->mode.y );
+			x + w, y + h, vga->mode->base.x, vga->mode->base.y );
 	}
 
 	uint8_t color_idx = get_color_index( color );
 
 	for( int yy = y; yy < y + h; yy++ ) {
-		uint8_t *addr = vga->base_addr + vga->mode.x * yy + x;
+		uint8_t *addr = vga->base_addr + vga->mode->base.x * yy + x;
 		memset( addr, color_idx, w );
 	}
 }
@@ -380,7 +347,7 @@ void vga_draw_rectangle( vga_t *vga, const int x, const int y, const int w, cons
 void vga_clear_screen( vga_t *vga, const vga_color_t color )
 {
 	memset( vga->base_addr, get_color_index( color ),
-		vga->mode.x * vga->mode.y );
+		vga->mode->base.x * vga->mode->base.y );
 }
 
 void vga_draw_char( vga_t *vga, const unsigned char c, const int x, const int y, const vga_color_t background, const vga_color_t foreground )
@@ -412,7 +379,7 @@ void vga_draw_char( vga_t *vga, const unsigned char c, const int x, const int y,
 				data[vga_font.Width-1-xx] = fg_color_idx;
 			}
 		}
-		uint8_t *addr = vga->base_addr + vga->mode.x * ( y + yy ) + x;
+		uint8_t *addr = vga->base_addr + vga->mode->base.x * ( y + yy ) + x;
 		memcpy( addr, data, vga_font.Width );
 	}
 }
@@ -432,14 +399,14 @@ void vga_use_z_buffer( vga_t *vga, bool use )
 	vga->use_z_buffer = use;
 
 	if( vga->use_z_buffer ) {
-		vga->zbuffer = (uint8_t *)malloc( vga->mode.segment_size );
+		vga->zbuffer = (uint8_t *)malloc( vga->mode->segment_size );
 		vga->base_addr = &vga->zbuffer[0];
 	} else {
 		if( vga->zbuffer != NULL ) {
 			free( vga->zbuffer );
 			vga->zbuffer = NULL;
 		}
-		vga->base_addr = vga->mode.segment;
+		vga->base_addr = vga->mode->segment;
 	}
 }
 
@@ -447,7 +414,7 @@ void vga_refresh( vga_t *vga )
 {
 	if( vga->use_z_buffer ) {
 		vga_wait_for_retrace( vga );
-		memcpy( vga->mode.segment, vga->zbuffer, vga->mode.segment_size );
+		memcpy( vga->mode->segment, vga->zbuffer, vga->mode->segment_size );
 	}
 }
 
diff --git a/src/drivers/video/vga.h b/src/drivers/video/vga.h
index 600180a..fed47a1 100644
--- a/src/drivers/video/vga.h
+++ b/src/drivers/video/vga.h
@@ -9,28 +9,19 @@
 #include "interrupts.h"
 #include "port.h"
 
-#include "driver.h"
+#include "video.h"
 
 #define NOF_MODE_REGS 66
 
-typedef enum {
-	VGA_MODE_TYPE_TEXT,
-	VGA_MODE_TYPE_GRAPHICS
-} vga_mode_type_t;
-
 typedef struct {
-	vga_mode_type_t mode_type;
-	int x;
-	int y;
-	int color_depth;
+	video_mode_t base;
 	uint8_t regs[NOF_MODE_REGS];
 	uint8_t *segment;
 	size_t segment_size;
 } vga_mode_t;
 
 typedef struct {
-	driver_t base;
-	interrupt_t *interrupts;
+	video_t base;
 	port8_t misc_port;
 	port8_t crtc_index_port;
 	port8_t crtc_data_port;
@@ -42,7 +33,7 @@ typedef struct {
 	port8_t attribute_controller_read_port;
 	port8_t attribute_controller_write_port;
 	port8_t attribute_controller_reset_port;
-	vga_mode_t mode;
+	vga_mode_t *mode;
 	bool use_z_buffer;
 	uint8_t *zbuffer;
 	// stores either the address to the beginning of the segment
@@ -51,7 +42,7 @@ typedef struct {
 } vga_t;
 
 typedef struct {
-	driver_vtable_t base;
+	video_vtable_t base;
 } vga_vtable_t;
 
 void vga_init( vga_t *vga, interrupt_t *interrupt, void *context );
@@ -60,9 +51,7 @@ void vga_deactivate( void *obj );
 void vga_deinit( void *obj );
 void vga_print_info( void *obj );
 
-vga_mode_t vga_make_mode( const vga_mode_type_t mode_type, const int x, const int y, const int color_depth );
-bool vga_set_mode( vga_t *vga, const vga_mode_t mode );
-bool vga_supports_mode( const vga_mode_t mode );
+bool vga_switch_mode( void *obj, const video_mode_t *mode );
 
 typedef struct {
 	int R;
diff --git a/src/drivers/video/video.c b/src/drivers/video/video.c
index eb12272..7e062a5 100644
--- a/src/drivers/video/video.c
+++ b/src/drivers/video/video.c
@@ -20,6 +20,8 @@ void video_init( video_t *video, interrupt_t *interrupt, void *context )
 
 	driver_init( (driver_t *)video, DRIVER_TYPE_VIDEO, interrupt, context );
 
+	video->nof_modes = 0;
+
 	((driver_t *)video)->vtable = (driver_vtable_t *)&video_vtable;
 }
 
@@ -42,3 +44,76 @@ void video_print_info( void *obj )
 {
 	kernel_panic( "Printing info of generic video driver should not be called directly." );
 }
+
+video_mode_t video_make_mode( const video_mode_type_t mode_type, const int x, const int y, const int color_depth )
+{
+	video_mode_t mode;
+
+	mode.mode_type = mode_type;
+	mode.x = x;
+	mode.y = y;
+	mode.color_depth = color_depth;
+
+	return mode;
+}
+
+void video_register_mode( void *obj, const video_mode_t *mode )
+{
+	video_t *video = (video_t *)obj;
+
+	if( video->nof_modes >= MAX_NOF_VIDEO_MODES ) {
+		kernel_panic( "Trying to register too many video modes, see MAX_NOF_VIDEO_MODES: %d", MAX_NOF_VIDEO_MODES );
+	}
+
+	video->modes[video->nof_modes++] = mode;
+}
+
+static int get_matching_mode_idx( video_t *video, const video_mode_t mode )
+{
+	for( int i = 0; video->modes[i]->x != 0; i++ ) {
+		if( 	mode.mode_type == video->modes[i]->mode_type &&
+			mode.x == video->modes[i]->x &&
+			mode.y == video->modes[i]->y &&
+			mode.color_depth == video->modes[i]->color_depth ) {
+			return i;
+		}
+	}
+
+	return -1;
+}
+
+bool video_supports_mode( void *obj, const video_mode_t mode )
+{
+	video_t *video = (video_t *)obj;
+
+	for( int i = 0; video->modes[i]->x != 0; i++ ) {
+		if( 	mode.mode_type == video->modes[i]->mode_type &&
+			mode.x == video->modes[i]->x &&
+			mode.y == video->modes[i]->y &&
+			mode.color_depth == video->modes[i]->color_depth ) {
+			return true;
+		}
+	}
+
+	return false;
+}
+
+bool video_set_mode( void *obj, const video_mode_t mode )
+{
+	video_t *video = (video_t *)obj;
+
+	// do not allow unknown timings!
+	if( !((video_vtable_t *)(video->base.vtable))->supports_mode( obj, mode ) ) {
+		return false;
+	}
+
+	const video_mode_t *matching_mode = video->modes[get_matching_mode_idx( video, mode )];
+
+	return ((video_vtable_t *)(video->base.vtable))->switch_mode( obj, matching_mode );
+}
+
+bool video_switch_mode( void *obj, const video_mode_t *mode )
+{
+	kernel_panic( "Switching mode function of abstract video driver should not be called directly." );
+}
+
diff --git a/src/drivers/video/video.h b/src/drivers/video/video.h
index 713aa4f..d17a51d 100644
--- a/src/drivers/video/video.h
+++ b/src/drivers/video/video.h
@@ -3,12 +3,34 @@
 
 #include "driver.h"
 
+#include <stdbool.h>
+
+typedef enum {
+	VIDEO_MODE_TYPE_TEXT,
+	VIDEO_MODE_TYPE_GRAPHICS
+} video_mode_type_t;
+
+#define MAX_NOF_VIDEO_MODES 255
+
+typedef struct {
+	video_mode_type_t mode_type;
+	int x;
+	int y;
+	int color_depth;
+} video_mode_t;
+
 typedef struct {
 	driver_t base;
+	unsigned int nof_modes;
+	const video_mode_t *modes[MAX_NOF_VIDEO_MODES];
 } video_t;
 
 typedef struct {
 	driver_vtable_t base;
+	void (*register_mode)( void *obj, const video_mode_t *mode );
+	bool (*supports_mode)( void *obj, const video_mode_t mode );
+	bool (*set_mode)( void *obj, const video_mode_t mode );
+	bool (*switch_mode)( void *obj, const video_mode_t *mode );
 } video_vtable_t;
 
 void video_init( video_t *video, interrupt_t *interrupt, void *context );
@@ -17,4 +39,11 @@ void video_deactivate( void *obj );
 void video_deinit( void *obj );
 void video_print_info( void *obj );
 
+video_mode_t video_make_mode( const video_mode_type_t mode_type, const int x, const int y, const int color_depth );
+
+void video_register_mode( void *obj, const video_mode_t *mode );
+bool video_supports_mode( void *obj, const video_mode_t mode );
+bool video_set_mode( void *obj, const video_mode_t mode );
+bool video_switch_mode( void *obj, const video_mode_t *mode );
+
 #endif // VIDEO_H
diff --git a/src/gui/desktop.c b/src/gui/desktop.c
index 9851b78..e0cb69b 100644
--- a/src/gui/desktop.c
+++ b/src/gui/desktop.c
@@ -49,13 +49,13 @@ void desktop_draw( void *obj, graphics_context_t *context )
 		if( desktop->mouse_x > i ) {
 			vga_set_pixel( context, desktop->mouse_x - i, desktop->mouse_y, VGA_COLOR_WHITE );
 		}
-		if( desktop->mouse_x < context->mode.x - i ) {
+		if( desktop->mouse_x < context->mode->base.x - i ) {
 			vga_set_pixel( context, desktop->mouse_x + i, desktop->mouse_y, VGA_COLOR_WHITE );
 		}
 		if( desktop->mouse_y > i ) {
 			vga_set_pixel( context, desktop->mouse_x, desktop->mouse_y - i, VGA_COLOR_WHITE );
 		}
-		if( desktop->mouse_y < context->mode.y - i ) {
+		if( desktop->mouse_y < context->mode->base.y - i ) {
 			vga_set_pixel( context, desktop->mouse_x, desktop->mouse_y + i, VGA_COLOR_WHITE );
 		}
 	}
diff --git a/src/gui/window.c b/src/gui/window.c
index fd53920..681c3b7 100644
--- a/src/gui/window.c
+++ b/src/gui/window.c
@@ -39,14 +39,14 @@ void window_draw( void *obj, graphics_context_t *context )
 	if( ((widget_t *)widget)->x < 0 ) {
 		((widget_t *)widget)->x = 0;
 	}
-	if( ((widget_t *)widget)->x > context->mode.x - ((widget_t *)widget)->w ) {
-		((widget_t *)widget)->x = context->mode.x - ((widget_t *)widget)->w;
+	if( ((widget_t *)widget)->x > context->mode->base.x - ((widget_t *)widget)->w ) {
+		((widget_t *)widget)->x = context->mode->base.x - ((widget_t *)widget)->w;
 	}
 	if( ((widget_t *)widget)->y < 0 ) {
 		((widget_t *)widget)->y = 0;
 	}
-	if( ((widget_t *)widget)->y > context->mode.y - ((widget_t *)widget)->h ) {
-		((widget_t *)widget)->y = context->mode.y - ((widget_t *)widget)->h;
+	if( ((widget_t *)widget)->y > context->mode->base.y - ((widget_t *)widget)->h ) {
+		((widget_t *)widget)->y = context->mode->base.y - ((widget_t *)widget)->h;
 	}
 
 	composite_widget_draw( obj, context );
diff --git a/src/kernel/kernel.c b/src/kernel/kernel.c
index 4f68f18..102fb69 100644
--- a/src/kernel/kernel.c
+++ b/src/kernel/kernel.c
@@ -348,7 +348,8 @@ static void switch_to_graphics_mode( global_context_t *global_context )
 	mouse_t *mouse = global_context->mouse;
 	desktop_t *desktop = &global_context->desktop;
 
-	if( vga_set_mode( vga, vga_make_mode( VGA_MODE_TYPE_GRAPHICS, 320, 200, 8 ) ) ) {
+	video_mode_t mode = video_make_mode( VIDEO_MODE_TYPE_GRAPHICS, 320, 200, 8 );
+	if( ((video_vtable_t *)(vga->base.base.vtable))->set_mode( vga, mode ) ) {
 		vga_text_save( vga_text );
 
 		desktop_init( desktop, 320, 200, VGA_COLOR_BLUE );
@@ -368,13 +369,13 @@ static void switch_to_graphics_mode( global_context_t *global_context )
 		}
 		*p = '\0';
 
-		window_init( &global_context->window3, (widget_t *)desktop, 55, 5, vga->mode.x - 65, 100, VGA_COLOR_CYAN );
+		window_init( &global_context->window3, (widget_t *)desktop, 55, 5, vga->mode->base.x - 65, 100, VGA_COLOR_CYAN );
 		((composite_widget_vtable_t *)global_context->desktop.base.base.vtable)->add_child( desktop, (widget_t *)&global_context->window3 );
 
 		text_widget_init( &global_context->widget3, (widget_t *)&global_context->window3, 1, 1, global_context->window3.base.base.w - 2, global_context->window3.base.base.h - 2, VGA_COLOR_RED, s );
 		((composite_widget_vtable_t *)global_context->window3.base.base.vtable)->add_child( (composite_widget_t *)&global_context->window3, (widget_t *)&global_context->widget3 );
 
-		((mouse_vtable_t *)(mouse->base.vtable))->set_resolution( mouse, vga->mode.x, vga->mode.y );
+		((mouse_vtable_t *)(mouse->base.vtable))->set_resolution( mouse, vga->mode->base.x, vga->mode->base.y );
 
 		// enable Z buffering
 		vga_use_z_buffer( global_context->vga, true );
@@ -391,7 +392,8 @@ static void switch_to_text_mode( global_context_t *global_context )
 
 	vga_text_restore( vga_text );
 
-	if( vga_set_mode( vga, vga_make_mode( VGA_MODE_TYPE_TEXT, 640, 480, 4 ) ) ) {
+	video_mode_t mode = video_make_mode( VIDEO_MODE_TYPE_TEXT, 640, 480, 4 );
+	if( ((video_vtable_t *)(vga->base.base.vtable))->set_mode( vga, mode ) ) {
 		vga_text_set_cursor( vga_text, vga_text->cursor_x, vga_text->cursor_y );
 		((mouse_vtable_t *)(mouse->base.vtable))->set_resolution( mouse, vga_text->res_x, vga_text->res_y );
 		global_context->mode = MODE_TEXT;