Frontend.XF/{ReceivePage,FEHelpers}: add bits/sats

With this new TapGestureRecognizer, we allow the user to tap on
the BTC amount and switch to bits and sats (and back to BTC if
she taps a 3rd time).

src/GWallet.Frontend.XF/FrontendHelpers.fs

@@ -38,6 +38,15 @@ type internal CurrencyImageSize =
 
 module FrontendHelpers =
 
+    type CryptoSubUnit =
+    | No
+    | Specific of multiplier:int * caption:string
+
+    let Sats =
+        CryptoSubUnit.Specific(100_000_000, "sats")
+    let Bits =
+        CryptoSubUnit.Specific(1_000_000, "bits")
+
     type IGlobalAppState =
         [<CLIEvent>]
         abstract member Resumed: IEvent<unit> with get
@@ -109,6 +118,7 @@ module FrontendHelpers =
 
     let UpdateBalance (balance: MaybeCached<decimal>) currency usdRate
                       (maybeFrame: Option<Frame>) (balanceLabel: Label) (fiatBalanceLabel: Label)
+                      (cryptoSubUnit: CryptoSubUnit)
                           : MaybeCached<decimal> =
         let maybeBalanceAmount =
             match balance with
@@ -129,8 +139,18 @@ module FrontendHelpers =
             | None ->
                 SPrintF1 "%A (?)" currency, NotFresh(NotAvailable), SPrintF1 "(?) %s" defaultFiatCurrency
             | Some balanceAmount ->
-                let cryptoAmount = Formatting.DecimalAmountRounding CurrencyType.Crypto balanceAmount
-                let cryptoAmountStr = SPrintF2 "%A %s" currency cryptoAmount
+                let adjustedBalance =
+                    match cryptoSubUnit with
+                    | No -> balanceAmount
+                    | Specific (multiplier, _caption) ->
+                        balanceAmount * decimal multiplier
+                let cryptoAmount = Formatting.DecimalAmountRounding CurrencyType.Crypto adjustedBalance
+                let cryptoAmountStr =
+                    match cryptoSubUnit with
+                    | No ->
+                        SPrintF2 "%A %s" currency cryptoAmount
+                    | Specific (_multiplier, caption) ->
+                        SPrintF2 "%s %A" cryptoAmount caption
                 let fiatAmount,fiatAmountStr = BalanceInUsdString balanceAmount usdRate
                 cryptoAmountStr,fiatAmount,fiatAmountStr
         MainThread.BeginInvokeOnMainThread(fun _ ->
@@ -159,6 +179,7 @@ module FrontendHelpers =
                               (Some balanceSet.Widgets.Frame)
                               balanceSet.Widgets.CryptoLabel
                               balanceSet.Widgets.FiatLabel
+                              CryptoSubUnit.No
             return {
                 BalanceSet = balanceSet
                 FiatAmount = fiatAmount
@@ -187,6 +208,7 @@ module FrontendHelpers =
                                       (Some balanceSet.Widgets.Frame)
                                       balanceSet.Widgets.CryptoLabel
                                       balanceSet.Widgets.FiatLabel
+                                      CryptoSubUnit.No
                     return {
                         BalanceSet = balanceSet
                         FiatAmount = fiatAmount

src/GWallet.Frontend.XF/ReceivePage.xaml.fs

@@ -33,6 +33,27 @@ type ReceivePage(account: IAccount,
     let currencyImg =
         mainLayout.FindByName<Image> "currencyImage"
 
+    let balanceLabel = mainLayout.FindByName<Label> "balanceLabel"
+    let fiatBalanceLabel = mainLayout.FindByName<Label> "fiatBalanceLabel"
+
+    let tapCryptoLabel accountBalance =
+        let cryptoSubUnit =
+            if balanceLabel.Text.StartsWith "BTC" then
+                FrontendHelpers.Bits
+            elif balanceLabel.Text.EndsWith "bits" then
+                FrontendHelpers.Sats
+            else
+                FrontendHelpers.CryptoSubUnit.No
+        FrontendHelpers.UpdateBalance
+            (NotFresh accountBalance)
+            account.Currency
+            usdRate
+            None
+            balanceLabel
+            fiatBalanceLabel
+            cryptoSubUnit
+        |> ignore
+
     do
         self.Init()
 
@@ -44,12 +65,17 @@ type ReceivePage(account: IAccount,
                         { CryptoLabel = null; FiatLabel = null ; Frame = null })
 
     member __.Init() =
-        let balanceLabel = mainLayout.FindByName<Label>("balanceLabel")
-        let fiatBalanceLabel = mainLayout.FindByName<Label>("fiatBalanceLabel")
 
         let accountBalance =
             Caching.Instance.RetrieveLastCompoundBalance account.PublicAddress account.Currency
-        FrontendHelpers.UpdateBalance (NotFresh accountBalance) account.Currency usdRate None balanceLabel fiatBalanceLabel
+        FrontendHelpers.UpdateBalance
+            (NotFresh accountBalance)
+            account.Currency
+            usdRate
+            None
+            balanceLabel
+            fiatBalanceLabel
+            FrontendHelpers.CryptoSubUnit.No
             |> ignore
 
         // this below is for the case when a new ReceivePage() instance is suddenly created after sending a transaction
@@ -60,11 +86,19 @@ type ReceivePage(account: IAccount,
                                       (Some balanceWidgetsFromBalancePage.Frame)
                                       balanceWidgetsFromBalancePage.CryptoLabel
                                       balanceWidgetsFromBalancePage.FiatLabel
+                                      FrontendHelpers.CryptoSubUnit.No
             |> ignore
 
         balanceLabel.FontSize <- FrontendHelpers.BigFontSize
         fiatBalanceLabel.FontSize <- FrontendHelpers.MediumFontSize
 
+        if account.Currency = Currency.BTC then
+            let cryptoTapGestureRecognizer = TapGestureRecognizer()
+            cryptoTapGestureRecognizer.Tapped.Subscribe(
+                fun _ -> tapCryptoLabel accountBalance
+            ) |> ignore
+            balanceLabel.GestureRecognizers.Add cryptoTapGestureRecognizer
+
         let qrCode = mainLayout.FindByName<ZXingBarcodeImageView> "qrCode"
         if isNull qrCode then
             failwith "Couldn't find QR code"