9. Screen and Coordinates

9.1 Screen

• The part within the window where the background color can be changed is called the screen (scene)
• Siv3D can display text, shapes, and images in this area
• The screen size is 800 pixels wide and 600 pixels tall by default
• The screen size may also be called "window size"
  • The window size including the frame around the screen, such as the title bar, is called "window area size" to distinguish it
• In normal Siv3D programming, it's sufficient to be aware of only the screen size (window size)

9.2 Changing Screen Size

• Change the screen size with Window::Resize(width, height)
• Once changed, that size is maintained. Usually set at the beginning before the main loop
• The following code changes the screen size to 1280 pixels wide and 720 pixels tall

Change Screen Size

# include <Siv3D.hpp>

void Main()
{
	// Resize screen to 1280x720
	Window::Resize(1280, 720);

	while (System::Update())
	{

	}
}

9.3 Coordinates

• When displaying shapes and images on the screen, you specify coordinates that represent pixel positions on the screen
• Coordinates are represented as (X, Y) using two values: X coordinate and Y coordinate
• The top-left pixel of the screen has "X coordinate: 0" and "Y coordinate: 0", which is (0, 0)
• Moving right increases the X coordinate, and moving down increases the Y coordinate
• When the screen size is 800 × 600, the bottom-right pixel of the screen has coordinates (799, 599)

• The following code displays the coordinates of the mouse cursor in the top-left of the screen

Display Mouse Cursor Coordinates

# include <Siv3D.hpp>

void Main()
{
	while (System::Update())
	{
		ClearPrint();

		// Display current mouse cursor coordinates
		Print << Cursor::Pos();
	}
}

9.4 Classes for Representing Coordinates

• The classes Point and Vec2 are provided for representing coordinates
• Point represents coordinates with integers

struct Point
{
	int32 x;
	int32 y;
};

• Vec2 represents coordinates with floating point numbers

struct Vec2
{
	double x;
	double y;
};

• Cursor::Pos() introduced in 9.3 returns the mouse cursor coordinates as a Point type

Display Mouse Cursor Coordinates

# include <Siv3D.hpp>

void Main()
{
	while (System::Update())
	{
		ClearPrint();

		const Point pos = Cursor::Pos();

		// Display current mouse cursor coordinates separated by X and Y coordinates
		Print << U"X: " << pos.x;
		Print << U"Y: " << pos.y;
	}
}

9.5 Converting Point → Vec2

• Point → Vec2 can be converted naturally (implicitly)

# include <Siv3D.hpp>

void Main()
{
	while (System::Update())
	{
		ClearPrint();

		const Vec2 pos = Cursor::Pos();

		// Display current mouse cursor coordinates separated by X and Y coordinates
		Print << U"X: " << pos.x;
		Print << U"Y: " << pos.y;
	}
}

9.6 Converting Vec2 → Point

• Converting Vec2 → Point loses information, so you need to convert explicitly using .asPoint()
• Decimal information is truncated

# include <Siv3D.hpp>

void Main()
{
	const Vec2 pos1{ 123.4, 567.8 };

	Print << pos1;

	// Convert Vec2 → Point
	const Point pos2 = pos1.asPoint();

	Print << pos2;

	while (System::Update())
	{

	}
}

Review Checklist

• Understood the default screen size (800x600)
• Learned that screen size can be changed with Window::Resize(width, height)
• Understood that coordinates are represented by two values, X and Y coordinates, with the top-left of the screen being (0, 0)
• Learned that Point and Vec2 are classes for representing coordinates, where Point uses integers and Vec2 uses floating point numbers
• Learned that Point → Vec2 can be converted implicitly
• Learned that Vec2 → Point is converted explicitly using .asPoint()