Layout improvements: do not draw the stopwatch if there is not

enough room for it.

main.go

@@ -300,10 +300,8 @@ func eventloop() {
 	}
 
 	swidth := new(int)
-	*swidth = 900
 	hrpage = func() {
 		stopbtn := func() {
-			gtx.Constraints.Width.Min = *swidth
 			gtx.Constraints.Height.Min = 100
 			layout.UniformInset(unit.Dp(2)).Layout(gtx, func() {
 				th.Button("Disconnect").Layout(gtx, backBtn)
@@ -325,7 +323,10 @@ func eventloop() {
 							*swidth = s2
 						}
 					})
-					c3 := f3.Rigid(gtx, stopwatch)
+					var c3 layout.FlexChild
+					if gtx.Constraints.Width.Max > 370 {
+						c3 = f3.Rigid(gtx, stopwatch)
+					}
 					c4 := f3.Rigid(gtx, stopbtn)
 					f3.Layout(gtx,
 						c1,
@@ -346,19 +347,37 @@ func eventloop() {
 					stopwatch()
 				})
 			})
+			swheight := gtx.Dimensions.Size.Y
 			c2 := f.Rigid(gtx, func() {
-				layout.Align(layout.Center).Layout(gtx, stopbtn)
+				layout.Align(layout.Center).Layout(gtx, func() {
+					gtx.Constraints.Width.Min = *swidth
+					gtx.Constraints.Width.Max = *swidth
+					stopbtn()
+				})
 			})
-			f.Layout(gtx,
+			if gtx.Constraints.Height.Max < 775 {
-				f.Rigid(gtx, appname),
+				gtx.Constraints.Height.Max += swheight
-				f.Rigid(gtx, appstate),
+				f.Layout(gtx,
-				f.Rigid(gtx, periphname),
+					f.Rigid(gtx, appname),
-				f.Flex(gtx, 1.0, func() {
+					f.Rigid(gtx, appstate),
-					*swidth = hrcircle()
+					f.Rigid(gtx, periphname),
-				}),
+					f.Flex(gtx, 1.0, func() {
-				c1,
+						*swidth = hrcircle()
-				c2,
+					}),
-			)
+					c2,
+				)
+			} else {
+				f.Layout(gtx,
+					f.Rigid(gtx, appname),
+					f.Rigid(gtx, appstate),
+					f.Rigid(gtx, periphname),
+					f.Flex(gtx, 1.0, func() {
+						*swidth = hrcircle()
+					}),
+					c1,
+					c2,
+				)
+			}
 		}
 		if backBtn.Clicked(gtx) {
 			ble.Disconnect(periph)