add example

examples/core/2d_camera_mouse_zoom/go.mod

@@ -0,0 +1,11 @@
+module example
+
+go 1.19
+
+require (
+	github.com/gen2brain/raylib-go/raygui v0.0.0-20221122151443-e8a384ed1346
+	github.com/gen2brain/raylib-go/raylib v0.0.0-20221122155035-fe6d2c0ed32a
+)
+
+replace github.com/gen2brain/raylib-go/raylib => ../../../raylib
+replace github.com/gen2brain/raylib-go/raygui => ../../../raygui

examples/core/2d_camera_mouse_zoom/main.go

@@ -0,0 +1,105 @@
+package main
+
+import (
+	"github.com/gen2brain/raylib-go/raylib"
+)
+
+/*******************************************************************************************
+*
+*   raylib [core] example - 2d camera mouse zoom
+*
+*   Example originally created with raylib 4.2, last time updated with raylib 4.2
+*
+*   Example licensed under an unmodified zlib/libpng license, which is an OSI-certified,
+*   BSD-like license that allows static linking with closed source software
+*
+*   Copyright (c) 2022 Jeffery Myers (@JeffM2501)
+*
+********************************************************************************************/
+
+//------------------------------------------------------------------------------------
+// Program main entry point
+//------------------------------------------------------------------------------------
+func main() {
+	// Initialization
+	//--------------------------------------------------------------------------------------
+	const (
+		screenWidth  = 800
+		screenHeight = 450
+	)
+
+	rl.InitWindow(screenWidth, screenHeight, "raylib [core] example - 2d camera mouse zoom")
+
+	var camera rl.Camera2D
+	camera.Zoom = 1.0
+
+	rl.SetTargetFPS(60) // Set our game to run at 60 frames-per-second
+	//--------------------------------------------------------------------------------------
+
+	// Main game loop
+	for !rl.WindowShouldClose() { // Detect window close button or ESC key
+		// Update
+		//----------------------------------------------------------------------------------
+		// Translate based on mouse right click
+		if rl.IsMouseButtonDown(rl.MouseRightButton) {
+			delta := rl.GetMouseDelta()
+			delta = rl.Vector2Scale(delta, -1.0/camera.Zoom)
+
+			camera.Target = rl.Vector2Add(camera.Target, delta)
+		}
+
+		// Zoom based on mouse wheel
+		wheel := rl.GetMouseWheelMove()
+		if wheel != 0 {
+			// Get the world point that is under the mouse
+			mouseWorldPos := rl.GetScreenToWorld2D(rl.GetMousePosition(), camera)
+
+			// Set the offset to where the mouse is
+			camera.Offset = rl.GetMousePosition()
+
+			// Set the target to match, so that the camera maps the world space point
+			// under the cursor to the screen space point under the cursor at any zoom
+			camera.Target = mouseWorldPos
+
+			// Zoom increment
+			const zoomIncrement float32 = 0.125
+
+			camera.Zoom += (wheel * zoomIncrement)
+			if camera.Zoom < zoomIncrement {
+				camera.Zoom = zoomIncrement
+			}
+		}
+
+		//----------------------------------------------------------------------------------
+
+		// Draw
+		//----------------------------------------------------------------------------------
+		rl.BeginDrawing()
+		rl.ClearBackground(rl.Black)
+
+		rl.BeginMode2D(camera)
+
+		// Draw the 3d grid, rotated 90 degrees and centered around 0,0
+		// just so we have something in the XY plane
+		rl.PushMatrix()
+		rl.Translatef(0, 25*50, 0)
+		rl.Rotatef(90, 1, 0, 0)
+		rl.DrawGrid(100, 50)
+		rl.PopMatrix()
+
+		// Draw a reference circle
+		rl.DrawCircle(100, 100, 50, rl.Yellow)
+
+		rl.EndMode2D()
+
+		rl.DrawText("Mouse right button drag to move, mouse wheel to zoom", 10, 10, 20, rl.White)
+
+		rl.EndDrawing()
+		//----------------------------------------------------------------------------------
+	}
+
+	// De-Initialization
+	//--------------------------------------------------------------------------------------
+	rl.CloseWindow() // Close window and OpenGL context
+	//--------------------------------------------------------------------------------------
+}