From ff0040bbb1ccca58a210e160650fef3aa4de87f2 Mon Sep 17 00:00:00 2001
From: Sergio Vera Castellano <severa@magento.com>
Date: Fri, 12 Jan 2018 12:19:58 +0100
Subject: [PATCH] Small adjustments
---
.../parallax-scrolling-background/README.md | 4 +-
.../parallax-scrolling-background/main.go | 14 ++--
.../scrolling_background.go | 68 ++++++++++++-------
3 files changed, 55 insertions(+), 31 deletions(-)
diff --git a/examples/community/parallax-scrolling-background/README.md b/examples/community/parallax-scrolling-background/README.md
index 4c3b117..03ecfc6 100644
--- a/examples/community/parallax-scrolling-background/README.md
+++ b/examples/community/parallax-scrolling-background/README.md
@@ -2,6 +2,6 @@
Created by [Sergio Vera](https://github.com/svera)
-This example shows how to implement an infinite side scrolling background with a depth effect, using [parallax scrolling](https://en.wikipedia.org/wiki/Parallax_scrolling).
+This example shows how to implement an infinite side scrolling background with a depth effect, using [parallax scrolling](https://en.wikipedia.org/wiki/Parallax_scrolling). Code is based in the [infinite scrolling background](https://github.com/faiface/pixel/tree/master/examples/community/scrolling-background) demo.
-Credits to [Peter Hellberg](https://github.com/peterhellberg) for the reworked background image.
+Credits to [Peter Hellberg](https://github.com/peterhellberg) for the improved background images.
diff --git a/examples/community/parallax-scrolling-background/main.go b/examples/community/parallax-scrolling-background/main.go
index d74f367..a60b21c 100644
--- a/examples/community/parallax-scrolling-background/main.go
+++ b/examples/community/parallax-scrolling-background/main.go
@@ -29,8 +29,10 @@ const (
windowHeight = 450
foregroundHeight = 149
// This is the scrolling speed (pixels per second)
- backgroundSpeed = 60
- foregroundSpeed = 120
+ // Negative values will make background to scroll to the left,
+ // positive to the right.
+ backgroundSpeed = -60
+ foregroundSpeed = -120
)
func run() {
@@ -54,15 +56,15 @@ func run() {
panic(err)
}
- background := newScrollingBackground(picBackground, windowWidth, windowHeight, windowWidth)
- foreground := newScrollingBackground(picForeground, windowWidth, foregroundHeight, windowWidth)
+ background := NewScrollingBackground(picBackground, windowWidth, windowHeight, backgroundSpeed)
+ foreground := NewScrollingBackground(picForeground, windowWidth, foregroundHeight, foregroundSpeed)
last := time.Now()
for !win.Closed() {
dt := time.Since(last).Seconds()
last = time.Now()
- background.update(win, backgroundSpeed, dt)
- foreground.update(win, foregroundSpeed, dt)
+ background.Update(win, dt)
+ foreground.Update(win, dt)
win.Update()
}
}
diff --git a/examples/community/parallax-scrolling-background/scrolling_background.go b/examples/community/parallax-scrolling-background/scrolling_background.go
index 993c430..87ba83f 100644
--- a/examples/community/parallax-scrolling-background/scrolling_background.go
+++ b/examples/community/parallax-scrolling-background/scrolling_background.go
@@ -1,42 +1,64 @@
package main
import (
+ "math"
+
"github.com/faiface/pixel"
"github.com/faiface/pixel/pixelgl"
)
-type scrollingBackground struct {
- width float64
- height float64
- windowWidth float64
- displacementCounter float64
- backgrounds [2]*pixel.Sprite
- positions [2]pixel.Vec
+// ScrollingBackground stores all needed information to scroll a background
+// to the left or right
+type ScrollingBackground struct {
+ width float64
+ height float64
+ displacement float64
+ speed float64
+ backgrounds [2]*pixel.Sprite
+ positions [2]pixel.Vec
}
-func newScrollingBackground(pic pixel.Picture, width, height, windowWidth float64) *scrollingBackground {
- return &scrollingBackground{
- width: width,
- height: height,
- windowWidth: windowWidth,
+// NewScrollingBackground construct and returns a new instance of scrollingBackground,
+// positioning the background images according to the speed value
+func NewScrollingBackground(pic pixel.Picture, width, height, speed float64) *ScrollingBackground {
+ sb := &ScrollingBackground{
+ width: width,
+ height: height,
+ speed: speed,
backgrounds: [2]*pixel.Sprite{
pixel.NewSprite(pic, pixel.R(0, 0, width, height)),
pixel.NewSprite(pic, pixel.R(width, 0, width*2, height)),
},
- positions: [2]pixel.Vec{
- pixel.V(width/2, (height/2)+1),
- pixel.V(width+(width/2), (height/2)+1),
- },
+ }
+
+ sb.positionImages()
+ return sb
+}
+
+// If scrolling speed > 0, put second background image ouside the screen,
+// at the left side, otherwise put it at the right side.
+func (sb *ScrollingBackground) positionImages() {
+ if sb.speed > 0 {
+ sb.positions = [2]pixel.Vec{
+ pixel.V(sb.width/2, (sb.height/2)+1),
+ pixel.V((sb.width/2)-sb.width, (sb.height/2)+1),
+ }
+ } else {
+ sb.positions = [2]pixel.Vec{
+ pixel.V(sb.width/2, (sb.height/2)+1),
+ pixel.V(sb.width+(sb.width/2), (sb.height/2)+1),
+ }
}
}
-func (sb *scrollingBackground) update(win *pixelgl.Window, speed, dt float64) {
- if sb.displacementCounter <= -sb.windowWidth {
- sb.displacementCounter = 0
+// Update will move backgrounds certain pixels, depending of the amount of time passed
+func (sb *ScrollingBackground) Update(win *pixelgl.Window, dt float64) {
+ if math.Abs(sb.displacement) >= sb.width {
+ sb.displacement = 0
sb.positions[0], sb.positions[1] = sb.positions[1], sb.positions[0]
}
- d := pixel.V(-sb.displacementCounter, 0)
- sb.backgrounds[0].Draw(win, pixel.IM.Moved(sb.positions[0].Sub(d)))
- sb.backgrounds[1].Draw(win, pixel.IM.Moved(sb.positions[1].Sub(d)))
- sb.displacementCounter -= speed * dt
+ d := pixel.V(sb.displacement, 0)
+ sb.backgrounds[0].Draw(win, pixel.IM.Moved(sb.positions[0].Add(d)))
+ sb.backgrounds[1].Draw(win, pixel.IM.Moved(sb.positions[1].Add(d)))
+ sb.displacement += sb.speed * dt
}
--
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