Add support for SDL2 MultiGestureEvents

README.md

@@ -135,6 +135,24 @@ for pt := range render.IterLine(A, B) {
 * IterEllipse(A Point, B Point): draw an elipse fitting inside the
   rectangle bounded by points A and B.
 
+## Multitouch Gesture Notes
+
+Support for SDL2's MultiGestureEvent is added on October 6 2021.
+The event.State will have the property `Touching=true` while the engine
+believes multitouch gestures are afoot. This begins when the user touches
+the screen with two fingers, and _then_ motion is detected.
+
+SDL2 spams us with gesture events for each tiny change detected, and then
+just stops. The SDL driver in this repo doesn't set ev.State.Touching=false.
+One heuristic you may use in your program to detect when multitouch has
+ended is this:
+
+SDL2 always emulates the mouse Button1 click for one of the fingers.
+Record the position at the first Touching=true event, and monitor for
+delta changes in position as the "mouse cursor" moves. When delta
+movements become stale and don't update, you can set State.Touching=false
+in your program.
+
 ## License
 
 MIT.

color.go

@@ -19,6 +19,30 @@ var (
 	reHexColor8 = regexp.MustCompile(`^([A-Fa-f0-9]{2})([A-Fa-f0-9]{2})([A-Fa-f0-9]{2})([A-Fa-f0-9]{2})$`)
 )
 
+// Common color names.
+var (
+	Invisible  = Color{}
+	White      = RGBA(255, 255, 255, 255)
+	Grey       = RGBA(153, 153, 153, 255)
+	DarkGrey   = RGBA(64, 64, 64, 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)
+)
+
 // Color holds an RGBA color value.
 type Color struct {
 	Red   uint8

event/event.go

@@ -1,6 +1,8 @@
 package event
 
-import "strings"
+import (
+	"strings"
+)
 
 // State holds the current state of key/mouse events.
 type State struct {
@@ -30,6 +32,14 @@ type State struct {
 
 	// Window resized
 	WindowResized bool
+
+	// Touch state
+	Touching        bool
+	TouchNumFingers int
+	TouchCenterX    int
+	TouchCenterY    int
+	GestureRotated  float64
+	GesturePinched  float64
 }
 
 // NewState creates a new event.State.

interface.go

@@ -1,7 +1,6 @@
 package render
 
 import (
-	"fmt"
 	"image"
 
 	"git.kirsle.net/go/render/event"
@@ -51,148 +50,3 @@ type Texturer interface {
 	Size() Rect
 	Image() image.Image
 }
-
-// Rect has a coordinate and a width and height.
-type Rect struct {
-	X int
-	Y int
-	W int
-	H int
-}
-
-// NewRect creates a rectangle of size `width` and `height`. The X,Y values
-// are initialized to zero.
-func NewRect(width, height int) 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      int
-	PadX         int
-	PadY         int
-	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.PadX == 0 && t.PadY == 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)
-	DarkGrey   = RGBA(64, 64, 64, 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)
-)

rect.go

@@ -0,0 +1,102 @@
+package render
+
+import "fmt"
+
+// Rect has a coordinate and a width and height.
+type Rect struct {
+	X int
+	Y int
+	W int
+	H int
+}
+
+// NewRect creates a rectangle of size `width` and `height`. The X,Y values
+// are initialized to zero.
+func NewRect(width, height int) 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,
+	}
+}

sdl/events.go

@@ -11,6 +11,7 @@ import (
 // Debug certain SDL events
 var (
 	DebugWindowEvents = false
+	DebugTouchEvents  = false
 	DebugMouseEvents  = false
 	DebugClickEvents  = false
 	DebugKeyEvents    = false
@@ -22,6 +23,7 @@ func (r *Renderer) Poll() (*event.State, error) {
 
 	// Reset some events.
 	s.WindowResized = false
+	// s.Touching = false
 
 	// helper function to push keyboard key names on keyDown events only.
 	pushKey := func(name string, state uint8) {
@@ -105,6 +107,18 @@ func (r *Renderer) Poll() (*event.State, error) {
 					t.Timestamp, r.ticks, t.Type, t.Which, t.X, t.Y,
 				)
 			}
+		case *sdl.MultiGestureEvent:
+			if DebugTouchEvents {
+				fmt.Printf("[%d ms] tick:%d MultiGesture  type:%d  Num=%d  TouchID=%+v  Dt=%f  Dd=%f  XY=%f,%f\n",
+					t.Timestamp, r.ticks, t.Type, t.NumFingers, t.TouchID, t.DTheta, t.DDist, t.X, t.Y,
+				)
+			}
+			s.Touching = true
+			s.TouchNumFingers = int(t.NumFingers)
+			s.TouchCenterX = int(t.X)
+			s.TouchCenterY = int(t.Y)
+			s.GesturePinched = float64(t.DDist)
+			s.GestureRotated = float64(t.DTheta)
 		case *sdl.KeyboardEvent:
 			if DebugKeyEvents {
 				fmt.Printf("[%d ms] tick:%d Keyboard  type:%d  sym:%c  modifiers:%d  state:%d  repeat:%d\n",

text.go

@@ -0,0 +1,25 @@
+package render
+
+import "fmt"
+
+// Text holds information for drawing text.
+type Text struct {
+	Text         string
+	Size         int
+	Color        Color
+	Padding      int
+	PadX         int
+	PadY         int
+	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.PadX == 0 && t.PadY == 0 && t.Stroke == Invisible && t.Shadow == Invisible
+}