C++ Windows Forms L09 - GDI P2

C++.NET
Windows Forms Course
L09- GDI Part 2

Mohammad Shaker
mohammadshakergtr.wordpress.com
C++.NET Windows Forms Course
@ZGTRShaker

What do u need to draw sth?
• Pen(stroke width, color, etc)
• Paper
• Brush to filling your drawing

Drawing::Graphic
• Encapsulates a GDI* + drawing surface.
• This class cannot be inherited.

___________________
• GDI* : Graphical Device Interface

Drawing::Graphics

private: System::Void button1_Click_5(System::Object^
sender, System::EventArgs^ e)
{
Drawing::Graphics ^MyGraphics;
MyGraphics = pictureBox1->CreateGraphics();
}

Drawing::Graphics
private void DrawImagePointF(PaintEventArgs e)
{
// Create image.
Image newImage = Image.FromFile("SampImag.jpg");
// Create point for upper-left corner of image.
PointF ulCorner = new PointF(100.0F, 100.0F);
// Draw image to screen.
e.Graphics.DrawImage(newImage, ulCorner);
}

Drawing::Point
• What does this even mean? -_private: System::Void button1_Click(System::Object^
sender, System::EventArgs^ e)
{
button1->Location = 30,120;
}

Drawing::Point
• What will happen now?
private: System::Void button1_Click(System::Object^ sender,
System::EventArgs^ e)
{
Drawing::Point P;
P.X = 2;
P.Y = 23;
button1->Location = P;
}

System::Drawing::Pen
private: System::Void button1_Click_5(System::Object^ sender,
{
System::Drawing::Pen ^ MyPen = gcnew Pen(Color::Red);
}

Graphics.DrawLine Method
•
•
•
•

public: void DrawLine(Pen*, Point, Point);
public: void DrawLine(Pen*, PointF, PointF);
public: void DrawLine(Pen*, int, int, int, int);
public: void DrawLine(Pen*, float, float, float, float);

System::Drawing::Pen
{
Drawing::Graphics::DrawLine( MyPen, 2, 3, 4, 5);
}

System::Drawing
{
Drawing::Graphics::DrawLine( MyPen, 2, 3, 4,5 );
}

Compiler error

System::Drawing
{
MyGraphics->DrawLine( MyPen, 2, 3, 4,5 );
}

No compiler error but Runtime error when clicking button1

System::Drawing
private: System::Void button1_Click_5(System::Object^ sender, System::EventArgs^
e)
{
}
A line will be drawn!

System::Drawing
• After clicking the button

System::Drawing
• Can we do this?
{
MyGraphics->DrawLine(System::Drawing::Pen(Color::Red),2,3,50,105);
}
Compiler error

System::Drawing
• But remember we can just do this
private: System::Void button1_Click_5(System::Object^ sender, System::EventArgs^
e)
{
}

System::Drawing
{
Drawing::Point P1, P2;
P1.X = 50; P1.Y = 60;
P2.X = 150; P2.Y = 160;
MyGraphics->DrawLine( MyPen, P1, P2 );
P1.X = 50; P1.Y = 60;
P2.X = 510; P2.Y = 610;
}

System::Drawing
• What’s missing? Now we’ll find out!

System::Drawing
• Now, let’s have the following
{
Drawing::Point P1, P2;
P1.X = 50; P1.Y = 60;
P2.X = 150; P2.Y = 160;
P1.X = 50; P1.Y = 60;
P2.X = 510; P2.Y = 30;
}

System::Drawing
• Now, when scrolling the line should be appeared, right?

System::Drawing
• Now moving the scroll forward

Nothing!

System::Drawing
• Now moving the scroll backward

Nothing!

Control.Paint() Event
• Control.Paint Event
– Occurs when the control is redrawn

Control.Paint() Event

private: System::Void pictureBox1_Paint(System::Object^
sender, System::Windows::Forms::PaintEventArgs^ e)
{

}

System::Drawing
• How to solve this?!
– Storing the lines* we have in ??
• Linked list / List for example

– Then, when re-painting the pictureBox
• Re-drawing the hole line all over again!

____________________________________________________
* Note that we don’t have sth called “line” so we need to wrap it oursleves

System::Drawing
• Header of class Line
#pragma once
ref class Line
{
public:
System::Drawing::Point P1;
System::Drawing::Point P2;
Line();
Line(System::Drawing::Point p1, System::Drawing::Point p2);
};

System::Drawing
• cpp of class Line
#include "StdAfx.h"
#include "Line.h"
Line::Line()
{
P1 = System::Drawing::Point(0, 0);
P2 = System::Drawing::Point(0, 0);
}
Line::Line(System::Drawing::Point p1, System::Drawing::Point p2)
{
P1 = p1;
P2 = p2;
}

System::Drawing
• Back to Form1
private: Drawing::Graphics ^MyGraphics;
private: Pen ^MyPen;
private: System::Collections::Generic::LinkedList <Line^>
^ MyLinesList;

private: System::Void Form1_Load(System::Object^ sender,
{
MyPen = gcnew Pen(Color::Red);
MyLinesList = gcnew
System::Collections::Generic::LinkedList <Line^>;
}

System::Drawing
{
Drawing::Point P1(3,5);
Line^ L1 = gcnew Line(P1, P2);
MyLinesList->AddLast(L1);
Line^ L2 = gcnew Line(P3, P4);
MyLinesList->AddLast(L2);
}

System::Drawing
• Form1
{
for each(Line ^MyLine in MyLinesList)
{
Drawing::Point P1 = MyLine->P1;
Drawing::Point P2 = MyLine->P2;
MyGraphics->DrawLine(MyPen,P1, P2 );
}
}

System::Drawing
• Before clicking anything

System::Drawing
• After clicking button6 “filling the linkedList with values”

System::Drawing
• After starting to scroll which means start painting “repainting”
the pictureBox

System::Drawing
•

What should happen now after continuing to scroll?

System::Drawing
• Scroll Forward

System::Drawing
• Now, when re-scrolling back it’s there!

Clear Method
• Clears the entire drawing surface and fills it with the
specified background color.

Clear Method
• What happens now?
{
MyGraphics->Clear(Color::SkyBlue);
}

Refresh Method
{
pictureBox1->Refresh();
}

Refresh Method
• Now, when pressing “TRY” <<Refresh method caller>> button

Refresh Method
• When scrolling again!

Refresh Method
• Now, when pressing TRY again

Refresh Method
• We usually use Refresh method with timers to refresh the
data we have in the pictureBox
• But note!
– Refresh Method :
• Forces the control to invalidate its client area and immediately redraw
itself and any child controls.
– So that, now, when we refresh the pictureBox all the lines will be cleared!!!
– So we should store them and redraw them all over again in each paint!!!

private:
Rectangle RcDraw;
void Form1_MouseDown( Object^ /*sender*/, System::Windows::Forms::MouseEventArgs^ e )
{ // Determine the initial rectangle coordinates.
RcDraw.X = e->X; RcDraw.Y = e->Y; }
void Form1_MouseUp( Object^ /*sender*/, System::Windows::Forms::MouseEventArgs^ e )
{
// Determine the width and height of the rectangle.
if( e->X < RcDraw.X )
{ RcDraw.Width = RcDraw.X - e->X; RcDraw.X = e->X; }
else
{ RcDraw.Width = e->X - RcDraw.X; }
if( e->Y < RcDraw.Y )
{ RcDraw.Height = RcDraw.Y - e->Y; RcDraw.Y = e->Y; }
else
{ RcDraw.Height = e->Y - RcDraw.Y; }
// Force a repaint of the region occupied by the rectangle.
this->Invalidate( RcDraw );
}
void Form1_Paint( Object^ /*sender*/, System::Windows::Forms::PaintEventArgs^ e )
{ // Draw the rectangle.
float PenWidth = 5;
e->Graphics->DrawRectangle( gcnew Pen( Color::Blue,PenWidth ), RcDraw ); }

Graphics::Draw
• You can draw whatever you want!

Example : Graphics::DrawString
public:
void DrawStringRectangleF( PaintEventArgs^ e )
{
// Create string to draw.
String^ drawString = "Sample Text";
// Create font and brush.
System::Drawing::Font^ drawFont = gcnew System::Drawing::Font( "Arial",16 );
SolidBrush^ drawBrush = gcnew SolidBrush( Color::Black );
// Create rectangle for drawing.(FLOATING POINT NUMBERS)
float x = 150.0F;
float y = 150.0F;
float width = 200.0F;
float height = 50.0F;
RectangleF drawRect = RectangleF(x,y,width,height);

// Draw rectangle to screen.
Pen^ blackPen = gcnew Pen( Color::Black );
e->Graphics->DrawRectangle( blackPen, x, y, width, height );
// Draw string to screen.
e->Graphics->DrawString( drawString, drawFont, drawBrush, drawRect );
}

Drawing with timer
private: System::Void timer1_Tick(System::Object^ sender,
{
static int x1 = 0, x2 = 10;
static int y1 = 0, y2 = 10;
srand(time(0));
x2+= rand()%30; y2+=rand()%30;
MyGraphics->DrawLine(MyPen, x1, y1, x2, y2 );
x1 = x2; y1 = y2;
}
// We can use.

Random R;
int x2 = R.Next(150); // No seed

Drawing with timer
{
srand(time(0));
x2+= rand(); y2+=rand(); // no %30
x1 = x2; y1 = y2;
}

Drawing with timer
{
x2+= 30; y2+=10;
x1 = x2; y1 = y2;
}

Drawing with sleep
{
for(int i = 0; i < 10; i++)
{
srand(time(0));
x2+= rand()%40; y2+= rand()%30;
Threading::Thread::Sleep(1000);
x1 = x2; y1 = y2;
}
}

Drawing with sleep –
Refresh methods
• What will happens? :D
{
for(int i = 0; i < 10; i++)
{
srand(time(0));
x2+= rand()%40; y2+= rand()%30;
x1 = x2; y1 = y2;
}
}

Drawing with sleep –
Refresh methods

Refresh Method
• Remember :
– Refresh Method :
• Forces the control to invalidate its client area and immediately redraw
itself and any child controls.
– So that, now, when we refresh the pictureBox all the lines will be cleared!!!
– So we should store them and redraw them all over again in each paint!!!

Drawing with sleep and timer!
• What is that?!
{
srand(time(0));
x2+= rand()%30; y2+=rand()%30;
x1 = x2; y1 = y2;
}

• What is that?!
{
srand(time(0));
x2+= rand()%30; y2+=rand()%30;
x1 = x2; y1 = y2;
}

Now, every two
seconds a line will
be drawn and
cleared for another
one to be shown

Drawing with angles?
{
srand(time(0));
x2+= Math::Cos(rand())*20;
y2+= Math::Cos(rand())*20;
x1 = x2; y1 = y2;
}

public : Drawing::Pen ^MyPen;
{
srand(time(0));
x2+= Math::Cos(rand())*(rand()%30);
y2+= Math::Cos(rand())*(rand()%30);
x1 = x2;
y1 = y2;
}
};

• Precedence?
public : Drawing::Pen ^MyPen;
{
srand(time(0));
x2+= Math::Cos(rand())*rand()%30;
y2+= Math::Cos(rand())*rand()%30;
x1 = x2;
y1 = y2;
}
};
•Also remember that we can use for sincos
• Math::PI

Drawing And filling
• Brush :
– Defines objects used to fill the interiors of graphical shapes such as
rectangles, ellipses, pies, polygons, and paths.

Drawing And filling
{
Drawing::Rectangle MyRect(50,30,60,100);
Drawing::Brush ^MyBrush;
MyGraphics->FillEllipse(MyBrush, MyRect );
}
Compiler error

Drawing And filling
{
MyBrush = gcnew Drawing::Brush;
}
Compiler error

Drawing And filling
{
MyBrush = gcnew Drawing::SolidBrush(Color ::Yellow);
}

Drawing And filling
{
MyBrush = gcnew Drawing::SolidBrush(Color ::Brown);
}

Drawing And filling
{
MyGraphics = panel1->CreateGraphics();
MyBrush = gcnew Drawing::SolidBrush(Color ::Chocolate);
Drawing::Region ^MyRegion;
MyRegion = gcnew Drawing::Region(MyRect);
MyGraphics->FillRegion(MyBrush, MyRegion );
}

Drawing And filling
• Drawing on panel!

Event Handling
• Let’s have the following form

Event Handling
{
MessageBox::Show(sender->ToString());
}

Event Handling
{
MessageBox::Show(e->ToString());
}

Event Handling
• Now, let’s see this with pictureBox and paint event
– Run the project with the following code
private: System::Void pictureBox1_Paint(System::Object^ sender,
System::Windows::Forms::PaintEventArgs^ e)
{
MessageBox::Show(e->ToString());
}

After pressing ok for the first time

Another window re-open!

After pressing ok for the second time

Resize again, Nothing happens!, WHY?

Enlarge again and again and this continues.. But till when?

Use the console to trackdebug values!
Do not use messagebox for tracking!
(see it in utility slide)

Graphics.DrawBezier Method
• Draws a Bézier spline defined by four Point structures.
Name

Description

DrawBezier(Pen, Point, Point, Point, Point)

Draws a Bézier spline defined by four Point structures.

DrawBezier(Pen, PointF, PointF, PointF, PointF)

Draws a Bézier spline defined by four PointF structures.

DrawBezier(Pen, Single, Single, Single, Single, Single,
Single, Single, Single)

Draws a Bézier spline defined by four ordered pairs of coordinates that
represent points.

{
Pen ^ MyPen = gcnew Pen(Color::Red);
e->Graphics->DrawBezier(MyPen,20,20,50,50,90,90,70,70);
}

{
Pen ^ MyPen = gcnew Pen(Color::Red);
e->Graphics->DrawBezier(MyPen,20,20,50,90,90,90,70,70);
}

Region Class
• Describes the interior of a graphics shape composed of
rectangles and paths. This class cannot be inherited.
• Exclude Union Xor Intersect
• public: void Exclude( Rectangle rect )

Path
• Represents a series of connected lines and curves

LinearGradientBrush
Name
LinearGradientBrush(Point, Point, Color, Color)
LinearGradientBrush(PointF, PointF, Color, Color)
LinearGradientBrush(Rectangle, Color, Color,
LinearGradientMode)
LinearGradientBrush(Rectangle, Color, Color, Single)
LinearGradientBrush(RectangleF, Color, Color,
LinearGradientMode)
LinearGradientBrush(RectangleF, Color, Color, Single)

LinearGradientBrush(Rectangle, Color, Color, Single,
Boolean)
LinearGradientBrush(RectangleF, Color, Color, Single,
Boolean)

Description

Initializes a new instance of the LinearGradientBrush class with the
specified points and colors.
Initializes a new instance of the LinearGradientBrush class with the
specified points and colors.
Creates a new instance of the LinearGradientBrush class based on
a rectangle, starting and ending colors, and orientation.
a rectangle, starting and ending colors, and an orientation angle.
Creates a new instance of the LinearGradientBrush based on a
rectangle, starting and ending colors, and an orientation mode.

• How To draw this?

AddMetafileComment
BeginContainer

Adds a comment to the current Metafile object.
Overloaded. Saves a graphics container with the current state of this Graphics object
and opens and uses a new graphics container.
Clears the entire drawing surface and fills it with the specified background color.

ClearSupported by the.NET
Compact Framework.
CreateObjRef(inherited
Creates an object that contains all the relevant information required to generate a
proxy used to communicate with a remote object.
from MarshalByRefObject)
DisposeSupported by the.NET Releases all resources used by this Graphics object.
Compact Framework.
DrawArc
DrawBezier

Overloaded. Draws an arc representing a portion of an ellipse specified by a pair of
coordinates, a width, and a height.
Overloaded. Draws a Bzier spline defined by four Pointstructures.

DrawBeziers

Overloaded. Draws a series of Bzier splines from an array of Point structures.

DrawClosedCurve

Overloaded. Draws a closed cardinal spline defined by an array of Point structures.

DrawCurve

Overloaded. Draws a cardinal spline through a specified array of Point structures.

DrawEllipseSupported by
Overloaded. Draws an ellipse defined by a bounding rectangle specified by a pair of
the.NET Compact Framework. coordinates, a height, and a width.
DrawIconSupported by
Overloaded. Draws the image represented by the specified Icon object at the specified
the.NET Compact Framework. coordinates.

DrawIconUnstretched

Draws the image represented by the specified Icon object without scaling the
image.

DrawImageSupported by the.NET
Compact Framework.

Overloaded. Draws the specified Image object at the specified location and
with the original size.

DrawImageUnscaled

Overloaded. Draws the specified image using its original physical size at the
location specified by a coordinate pair.

DrawLineSupported by the.NET
Compact Framework.

Overloaded. Draws a line connecting the two points specified by coordinate
pairs.

DrawLines

Overloaded. Draws a series of line segments that connect an array
of Point structures.

DrawPath
DrawPie

Draws a GraphicsPath object.
Overloaded. Draws a pie shape defined by an ellipse specified by a coordinate
pair, a width, and a height and two radial lines.

DrawPolygonSupported by the.NET Overloaded. Draws a polygon defined by an array ofPoint structures.
Compact Framework.
DrawRectangleSupported by the.NET Overloaded. Draws a rectangle specified by a coordinate pair, a width, and a
Compact Framework.
height.
DrawRectangles

Overloaded. Draws a series of rectangles specified byRectangle structures.

DrawStringSupported by the.NET
Compact Framework.

Overloaded. Draws the specified text string at the specified location with the
specified Brush and Fontobjects.

EndContainer

EnumerateMetafile
Equals(inherited from Object)Supported
by the.NET Compact Framework.
ExcludeClip

Closes the current graphics container and restores the state of
this Graphics object to the state saved by a call to
the BeginContainer method.
Overloaded. Sends the records in the specified Metafileobject, one at a time,
to a callback method for display at a specified point.
Overloaded. Determines whether two Object instances are equal.

Overloaded. Updates the clip region of this Graphicsobject to exclude the
area specified by a Rectanglestructure.
FillClosedCurve
Overloaded. Fills the interior a closed cardinal spline curve defined by an
array of Point structures.
FillEllipseSupported by the.NET Compact Overloaded. Fills the interior of an ellipse defined by a bounding rectangle
Framework.
specified by a pair of coordinates, a width, and a height.
FillPath
Fills the interior of a GraphicsPath object.
FillPie
Overloaded. Fills the interior of a pie section defined by an ellipse specified
by a pair of coordinates, a width, and a height and two radial lines.
FillPolygonSupported by the.NET
Overloaded. Fills the interior of a polygon defined by an array of points
Compact Framework.
specified by Point structures.
FillRectangleSupported by the.NET
Overloaded. Fills the interior of a rectangle specified by a pair of coordinates,
Compact Framework.
a width, and a height.
FillRectangles
Overloaded. Fills the interiors of a series of rectangles specified
by Rectangle structures.
FillRegionSupported by the.NET Compact Fills the interior of a Region object.
Framework.

private:
void AddShadow( PaintEventArgs^ e )
{
// Create two SizeF objects.
SizeF shadowSize = listBox1->Size;
SizeF addSize = SizeF(10.5F,20.8F);

Adding Shadow!

// Add them together and save the result in shadowSize.
shadowSize = shadowSize + addSize;
// Get the location of the ListBox and convert it to a PointF.
PointF shadowLocation = listBox1->Location;
// Add two points to get a new location.
shadowLocation = shadowLocation + System::Drawing::Size( 5, 5 );
// Create a rectangleF.
RectangleF rectFToFill = RectangleF(shadowLocation,shadowSize);
// Create a custom brush using a semi-transparent color, and
// then fill in the rectangle.
Color customColor = Color::FromArgb( 50, Color::Gray );
SolidBrush^ shadowBrush = gcnew SolidBrush( customColor );
array<RectangleF>^ temp0 = {rectFToFill};
e->Graphics->FillRectangles( shadowBrush, temp0 );
// Dispose of the brush.
delete shadowBrush;
}

Drawing And filling - RegionData
• Example :
– The following example is designed for use with Windows Forms, and it
requires PaintEventArgse, which is a parameter of the Paint event
handler. The code performs the following actions:
•
•
•
•

Creates a rectangle and draw its to the screen in black.
Creates a region using the rectangle.
Gets the RegionData.
Draws the region data(an array of bytes) to the screen, by using the
DisplayRegionData helper function.

public:
void GetRegionDataExample( PaintEventArgs^ e )
{
// Create a rectangle and draw it to the screen in black.
Rectangle regionRect = Rectangle(20,20,100,100);
e->Graphics->DrawRectangle( Pens::Black, regionRect );

RegionData

// Create a region using the first rectangle.
System::Drawing::Region^ myRegion = gcnew System::Drawing::Region( regionRect );
// Get the RegionData for this region.
RegionData^ myRegionData = myRegion->GetRegionData();
int myRegionDataLength = myRegionData->Data->Length;
DisplayRegionData( e, myRegionDataLength, myRegionData );
}
void DisplayRegionData( PaintEventArgs^ e, int len, RegionData^ dat )
{ // Display the result.
int i;
float x = 20,y = 140;
System::Drawing::Font^ myFont = gcnew System::Drawing::Font( "Arial",8 );
SolidBrush^ myBrush = gcnew SolidBrush( Color::Black );
e->Graphics->DrawString( "myRegionData = ", myFont, myBrush, PointF(x,y) );
y = 160;
for( i = 0; i < len; i++ )
{
if( x > 300 )
{
y += 20;
x = 20;
}
e->Graphics->DrawString( dat->Data[ i ].ToString(), myFont, myBrush, PointF(x,y) );
x += 30;
}
}

C++ Windows Forms L09 - GDI P2

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