render/interface.go
Noah Petherbridge 243514f848 Centralized Tick Counter, Fix Actor Dragging Bug
* The game's tick counter was moved from Doodle.ticks to shmem.Tick
  where it is more easily available from every corner of the code.
* Fix a bug in the Level Editor where dragging an already-existing actor
  from one part of your map to another, would cause it to lose all its
  data (especially its UUID), breaking links to other doodads. Now the
  existing Actor catches a ride on the drag object to be reinserted
  later.
* Animate the Link Line visualizers between actors. They now animate a
  blinking color between magenta and grey-ish.
2019-07-05 16:04:36 -07:00

280 lines
6.1 KiB
Go

package render
import (
"fmt"
"image"
"math"
"git.kirsle.net/apps/doodle/lib/events"
)
// Engine is the interface for the rendering engine, keeping SDL-specific stuff
// far away from the core of Doodle.
type Engine interface {
Setup() error
// Poll for events like keypresses and mouse clicks.
Poll() (*events.State, error)
GetTicks() uint32
WindowSize() (w, h int)
// Present presents the current state to the screen.
Present() error
// Clear the full canvas and set this color.
Clear(Color)
SetTitle(string)
DrawPoint(Color, Point)
DrawLine(Color, Point, Point)
DrawRect(Color, Rect)
DrawBox(Color, Rect)
DrawText(Text, Point) error
ComputeTextRect(Text) (Rect, error)
// Texture caching.
StoreTexture(name string, img image.Image) (Texturer, error)
LoadTexture(name string) (Texturer, error)
Copy(t Texturer, src, dst Rect)
// Delay for a moment using the render engine's delay method,
// implemented by sdl.Delay(uint32)
Delay(uint32)
// Tasks that the Setup function should defer until tear-down.
Teardown()
Loop() error // maybe?
}
// Texturer is a stored image texture used by the rendering engine while
// abstracting away its inner workings.
type Texturer interface {
Size() Rect
}
// Rect has a coordinate and a width and height.
type Rect struct {
X int32
Y int32
W int32
H int32
}
// NewRect creates a rectangle of size `width` and `height`. The X,Y values
// are initialized to zero.
func NewRect(width, height int32) Rect {
return Rect{
W: width,
H: height,
}
}
func (r Rect) String() string {
return fmt.Sprintf("Rect<%d,%d,%d,%d>",
r.X, r.Y, r.W, r.H,
)
}
// Point returns the rectangle's X,Y values as a Point.
func (r Rect) Point() Point {
return Point{
X: r.X,
Y: r.Y,
}
}
// Bigger returns if the given rect is larger than the current one.
func (r Rect) Bigger(other Rect) bool {
// TODO: don't know why this is !
return !(other.X < r.X || // Lefter
other.Y < r.Y || // Higher
other.W > r.W || // Wider
other.H > r.H) // Taller
}
// Intersects with the other rectangle in any way.
func (r Rect) Intersects(other Rect) bool {
// Do a bidirectional compare.
compare := func(a, b Rect) bool {
var corners = []Point{
NewPoint(b.X, b.Y),
NewPoint(b.X, b.Y+b.H),
NewPoint(b.X+b.W, b.Y),
NewPoint(b.X+b.W, b.Y+b.H),
}
for _, pt := range corners {
if pt.Inside(a) {
return true
}
}
return false
}
return compare(r, other) || compare(other, r) || false
}
// IsZero returns if the Rect is uninitialized.
func (r Rect) IsZero() bool {
return r.X == 0 && r.Y == 0 && r.W == 0 && r.H == 0
}
// Add another rect.
func (r Rect) Add(other Rect) Rect {
return Rect{
X: r.X + other.X,
Y: r.Y + other.Y,
W: r.W + other.W,
H: r.H + other.H,
}
}
// Add a point to move the rect.
func (r Rect) AddPoint(other Point) Rect {
return Rect{
X: r.X + other.X,
Y: r.Y + other.Y,
W: r.W,
H: r.H,
}
}
// SubtractPoint is the inverse of AddPoint. Use this only if you need to invert
// the Point being added.
//
// This does r.X - other.X, r.Y - other.Y and keeps the width/height the same.
func (r Rect) SubtractPoint(other Point) Rect {
return Rect{
X: r.X - other.X,
Y: r.Y - other.Y,
W: r.W,
H: r.H,
}
}
// Text holds information for drawing text.
type Text struct {
Text string
Size int
Color Color
Padding int32
PadX int32
PadY int32
Stroke Color // Stroke color (if not zero)
Shadow Color // Drop shadow color (if not zero)
FontFilename string // Path to *.ttf file on disk
}
func (t Text) String() string {
return fmt.Sprintf(`Text<"%s" %dpx %s>`, t.Text, t.Size, t.Color)
}
// IsZero returns if the Text is the zero value.
func (t Text) IsZero() bool {
return t.Text == "" && t.Size == 0 && t.Color == Invisible && t.Padding == 0 && t.Stroke == Invisible && t.Shadow == Invisible
}
// Common color names.
var (
Invisible = Color{}
White = RGBA(255, 255, 255, 255)
Grey = RGBA(153, 153, 153, 255)
Black = RGBA(0, 0, 0, 255)
SkyBlue = RGBA(0, 153, 255, 255)
Blue = RGBA(0, 0, 255, 255)
DarkBlue = RGBA(0, 0, 153, 255)
Red = RGBA(255, 0, 0, 255)
DarkRed = RGBA(153, 0, 0, 255)
Green = RGBA(0, 255, 0, 255)
DarkGreen = RGBA(0, 153, 0, 255)
Cyan = RGBA(0, 255, 255, 255)
DarkCyan = RGBA(0, 153, 153, 255)
Yellow = RGBA(255, 255, 0, 255)
Orange = RGBA(255, 153, 0, 255)
DarkYellow = RGBA(153, 153, 0, 255)
Magenta = RGBA(255, 0, 255, 255)
Purple = RGBA(153, 0, 153, 255)
Pink = RGBA(255, 153, 255, 255)
)
// IterLine is a generator that returns the X,Y coordinates to draw a line.
// https://en.wikipedia.org/wiki/Digital_differential_analyzer_(graphics_algorithm)
func IterLine(x1, y1, x2, y2 int32) chan Point {
generator := make(chan Point)
go func() {
var (
dx = float64(x2 - x1)
dy = float64(y2 - y1)
)
var step float64
if math.Abs(dx) >= math.Abs(dy) {
step = math.Abs(dx)
} else {
step = math.Abs(dy)
}
dx = dx / step
dy = dy / step
x := float64(x1)
y := float64(y1)
for i := 0; i <= int(step); i++ {
generator <- Point{
X: int32(x),
Y: int32(y),
}
x += dx
y += dy
}
close(generator)
}()
return generator
}
// IterLine2 works with two Points rather than four coordinates.
func IterLine2(p1 Point, p2 Point) chan Point {
return IterLine(p1.X, p1.Y, p2.X, p2.Y)
}
// IterRect loops through all the points forming a rectangle between the
// top-left point and the bottom-right point.
func IterRect(p1, p2 Point) chan Point {
generator := make(chan Point)
go func() {
var (
TopLeft = p1
BottomRight = p2
TopRight = Point{
X: BottomRight.X,
Y: TopLeft.Y,
}
BottomLeft = Point{
X: TopLeft.X,
Y: BottomRight.Y,
}
)
// Trace all four edges and yield it.
var edges = []struct {
A Point
B Point
}{
{TopLeft, TopRight},
{TopLeft, BottomLeft},
{BottomLeft, BottomRight},
{TopRight, BottomRight},
}
for _, edge := range edges {
for pt := range IterLine2(edge.A, edge.B) {
generator <- pt
}
}
close(generator)
}()
return generator
}