add mouse zoom example (#2583)

examples/Makefile

@@ -375,6 +375,7 @@ CORE = \
     core/core_input_gestures \
     core/core_2d_camera \
     core/core_2d_camera_platformer \
+	core/core_2d_camera_mouse_zoom \
     core/core_3d_camera_mode \
     core/core_3d_camera_free \
     core/core_3d_camera_first_person \

examples/core/core_2d_camera_mouse_zoom.c

@@ -0,0 +1,101 @@
+/*******************************************************************************************
+*
+*   raylib [core] example - 2d camera mouse zoom
+*
+*   This example has been created using raylib 1.5 (www.raylib.com)
+*   raylib is licensed under an unmodified zlib/libpng license (View raylib.h for details)
+*
+*   Copyright (c) 2022 Jeffery Myers
+*
+********************************************************************************************/
+
+
+#include "raylib.h"
+#include "rlgl.h"
+#include "raymath.h";
+
+
+//------------------------------------------------------------------------------------
+// Program main entry point
+//------------------------------------------------------------------------------------
+int main ()
+{
+	// Initialization
+	//--------------------------------------------------------------------------------------
+	const int screenWidth = 800;
+	const int screenHeight = 450;
+
+	InitWindow(screenWidth, screenHeight, "raylib [core] example - 2d camera mouse zoom");
+
+	Camera2D camera = { 0 };
+	camera.zoom = 1;
+
+	SetTargetFPS(60);                   // Set our game to run at 60 frames-per-second
+	//--------------------------------------------------------------------------------------
+
+	// Main game loop
+	while (!WindowShouldClose())
+	{
+		// translate based on right click
+		if (IsMouseButtonDown(MOUSE_BUTTON_RIGHT))
+		{
+			Vector2 delta = GetMouseDelta();
+			delta = Vector2Scale(delta, -1.0f / camera.zoom);
+
+			camera.target = Vector2Add(camera.target, delta);
+		}
+
+		// zoom based on wheel
+		float wheel = GetMouseWheelMove();
+		if (wheel != 0)
+		{
+			// get the world point that is under the mouse
+			Vector2 mouseWorldPos = GetScreenToWorld2D(GetMousePosition(), camera);
+			
+			// set the offset to where the mouse is
+			camera.offset = 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
+			const float zoomIncrement = 0.125f;
+
+			camera.zoom += wheel * zoomIncrement;
+			if (camera.zoom < zoomIncrement)
+				camera.zoom = zoomIncrement;
+		}
+
+		//----------------------------------------------------------------------------------
+
+		// Draw
+		//----------------------------------------------------------------------------------
+		BeginDrawing();
+		BeginDrawing();
+		ClearBackground(BLACK);
+
+		BeginMode2D(camera);
+
+		// draw the 3d grid, rotated 90 degrees and centered around 0,0 just so we have something in the XY plane
+        rlPushMatrix();
+        rlTranslatef(0, 25 * 50, 0);
+        rlRotatef(90, 1, 0, 0);
+        DrawGrid(100, 50);
+        rlPopMatrix();
+
+		// draw a thing
+		DrawCircle(100, 100, 50, YELLOW);
+		EndMode2D();
+
+		DrawText("Right drag to move, mouse wheel to zoom", 2, 2, 20, WHITE);
+		
+		EndDrawing();
+		//----------------------------------------------------------------------------------
+	}
+
+	// De-Initialization
+    //--------------------------------------------------------------------------------------
+	CloseWindow();        // Close window and OpenGL context
+	//--------------------------------------------------------------------------------------
+	return 0;
+}