shithub: mycel

Info  •  Files  •  Log  •  Branches

smooth scroll

--- a/browser/scroll.go

+++ b/browser/scroll.go

@@ -23,6 +23,7 @@

 import (

 	"fmt"

 	"image"

+	"math"

 	"9fans.net/go/draw"

 	"github.com/mjl-/duit"

@@ -41,6 +42,7 @@

 	img           *draw.Image // for child to draw on

 	scrollbarSize int

 	lastMouseUI   duit.UI

+	drawOffset int

 }

 var _ duit.UI = &Scroll{}

@@ -126,7 +128,11 @@

 	if ui.childR.Empty() {

 		return

 	}

-	if ui.img == nil || ui.Kid.R.Size() != ui.img.R.Size() {

+	d := math.Abs(float64(ui.drawOffset - ui.Offset))

+	if  d > float64(ui.r.Max.Y) {

+		ui.Kid.Draw = duit.Dirty

+	}

+	if ui.img == nil || ui.drawRect().Size() != ui.img.R.Size() || ui.Kid.Draw == duit.Dirty {

 		var err error

 		if ui.img != nil {

 			ui.img.Free()

@@ -140,6 +146,7 @@

 		if duitError(dui, err, "allocimage") {

 			return

 		}

+		ui.drawOffset = ui.Offset

 	} else if ui.Kid.Draw == duit.Dirty {

 		ui.img.Draw(ui.img.R, dui.Background, nil, image.ZP)

 	}

@@ -157,7 +164,7 @@

 // Allocate only an image buffer of view size ui.r

 // - which is translated by scroll offset ui.Offset - instead

 // of whole Kid view size ui.Kid.R which leads to much

-// faster render times sometimes. Add same size rectangles

+// faster render times for large pages. Add same size rectangles

 // above/below to decrease flickering.

 func (ui *Scroll) drawRect() image.Rectangle {

 	if 2*ui.r.Dy() > ui.Kid.R.Dy() {

@@ -167,10 +174,10 @@

 		Min: ui.r.Min,

 		Max: image.Point{

 			ui.r.Max.X,

-			2*ui.r.Max.Y,

+			3*ui.r.Max.Y,

 		},

 	}

-	r = r.Add(image.Point{X:0, Y:ui.Offset})

+	r = r.Add(image.Point{X:0, Y:ui.Offset-ui.r.Max.Y})

 	if r.Min.Y > ui.Offset {

 		r.Min.Y -= ui.Offset

 	}