Set up basic camera functionality

moonpie/graphics/camera.lua

@@ -0,0 +1,37 @@
+-- Copyright (c) 2020 Trevor Redfern
+--
+-- This software is released under the MIT License.
+-- https://opensource.org/licenses/MIT
+
+local Camera = {}
+
+function Camera:new()
+  local c = setmetatable({}, { __index = Camera })
+  c.x = 0
+  c.y = 0
+  c.scale_x = 1
+  c.scale_y = 1
+  return c
+end
+
+function Camera:set_position(x, y)
+  self.x = x
+  self.y = y
+end
+
+function Camera:activate()
+  love.graphics.push()
+  love.graphics.translate(self.x, self.y)
+  love.graphics.scale(self.scale_x, self.scale_y)
+end
+
+function Camera:deactivate()
+  love.graphics.pop()
+end
+
+function Camera:scale(sx, sy)
+  self.scale_x = sx
+  self.scale_y = sy
+end
+
+return Camera

moonpie/graphics/camera_spec.lua

@@ -0,0 +1,48 @@
+-- Copyright (c) 2020 Trevor Redfern
+--
+-- This software is released under the MIT License.
+-- https://opensource.org/licenses/MIT
+
+describe("Camera", function()
+  local Camera = require "moonpie.graphics.camera"
+  local mock_love = require "moonpie.test_helpers.mock_love"
+
+  it("initializes to an inconsequential camera", function()
+    local c = Camera:new()
+    assert.equals(0, c.x)
+    assert.equals(0, c.y)
+    assert.equals(1, c.scale_x)
+    assert.equals(1, c.scale_y)
+  end)
+
+  it("pushes on the translation stack on activate", function()
+    mock_love.override_graphics("push", spy.new(function() end))
+    local c = Camera:new()
+    c:activate()
+    assert.spy(love.graphics.push).was.called()
+  end)
+
+  it("pops the stack when the camera is deactivated", function()
+    mock_love.override_graphics("pop", spy.new(function() end))
+    local c = Camera:new()
+    c:activate()
+    c:deactivate()
+    assert.spy(love.graphics.pop).was.called()
+  end)
+
+  it("translates based on the position of the camera", function()
+    mock_love.override_graphics("translate", spy.new(function() end))
+    local c = Camera:new()
+    c:set_position(43, 29)
+    c:activate()
+    assert.spy(love.graphics.translate).was.called_with(43, 29)
+  end)
+
+  it("scales the camera", function()
+    mock_love.override_graphics("scale", spy.new(function() end))
+    local c = Camera:new()
+    c:scale(10, 11)
+    c:activate()
+    assert.spy(love.graphics.scale).was.called_with(10, 11)
+  end)
+end)

moonpie/test_helpers/mock_love.lua

@@ -47,6 +47,7 @@ love = {
         push = function() end,
         rectangle = function(mode, x, y, w, h) end,
         reset = function() end,
+        scale = function() end,
         setCanvas = function() end,
         setColor = function() end,
         setFont = function() end,