Display an error text when ValueInput has invalid user input

src/qml/components/DeveloperOptions.qml

@@ -27,12 +27,19 @@ ColumnLayout {
         id: dbcacheSetting
         Layout.fillWidth: true
         header: qsTr("Database cache size (MiB)")
+        errorText: qsTr("This is not a valid cache size. Please choose a value between %1 and %2 MiB.").arg(optionsModel.minDbcacheSizeMiB).arg(optionsModel.maxDbcacheSizeMiB)
+        showErrorText: false
         actionItem: ValueInput {
             parentState: dbcacheSetting.state
             description: optionsModel.dbcacheSizeMiB
             onEditingFinished: {
-                optionsModel.dbcacheSizeMiB = parseInt(text)
-                dbcacheSetting.forceActiveFocus()
+                if (checkValidity(optionsModel.minDbcacheSizeMiB, optionsModel.maxDbcacheSizeMiB, parseInt(text))) {
+                    optionsModel.dbcacheSizeMiB = parseInt(text)
+                    dbcacheSetting.forceActiveFocus()
+                    dbcacheSetting.showErrorText = false
+                } else {
+                    dbcacheSetting.showErrorText = true
+                }
             }
         }
         onClicked: {
@@ -45,12 +52,19 @@ ColumnLayout {
         id: parSetting
         Layout.fillWidth: true
         header: qsTr("Script verification threads")
+        errorText: qsTr("This is not a valid thread count. Please choose a value between %1 and %2 threads.").arg(optionsModel.minScriptThreads).arg(optionsModel.maxScriptThreads)
+        showErrorText: !loadedItem.acceptableInput && loadedItem.length > 0
         actionItem: ValueInput {
             parentState: parSetting.state
             description: optionsModel.scriptThreads
             onEditingFinished: {
-                optionsModel.scriptThreads = parseInt(text)
-                parSetting.forceActiveFocus()
+                if (checkValidity(optionsModel.minScriptThreads, optionsModel.maxScriptThreads, parseInt(text))) {
+                    optionsModel.scriptThreads = parseInt(text)
+                    parSetting.forceActiveFocus()
+                    parSetting.showErrorText = false
+                } else {
+                    parSetting.showErrorText = true
+                }
             }
         }
         onClicked: {

src/qml/components/StorageSettings.qml

@@ -33,12 +33,19 @@ ColumnLayout {
         id: pruneTargetSetting
         Layout.fillWidth: true
         header: qsTr("Storage limit (GB)")
+        errorText: qsTr("This is not a valid prune target. Please choose a value that is equal to or larger than 1GB")
+        showErrorText: false
         actionItem: ValueInput {
             parentState: pruneTargetSetting.state
             description: optionsModel.pruneSizeGB
             onEditingFinished: {
-                optionsModel.pruneSizeGB = parseInt(text)
-                pruneTargetSetting.forceActiveFocus()
+                if (parseInt(text) < 1) {
+                    pruneTargetSetting.showErrorText = true
+                } else {
+                    optionsModel.pruneSizeGB = parseInt(text)
+                    pruneTargetSetting.forceActiveFocus()
+                    pruneTargetSetting.showErrorText = false
+                }
             }
         }
         onClicked: {

src/qml/controls/Header.qml

@@ -22,6 +22,7 @@ ColumnLayout {
     property string subtext: ""
     property int subtextMargin
     property int subtextSize: 15
+    property color subtextColor: Theme.color.neutral9
     property bool wrap: true
 
     spacing: 0
@@ -64,7 +65,7 @@ ColumnLayout {
             font.family: "Inter"
             font.styleName: "Regular"
             font.pixelSize: root.subtextSize
-            color: Theme.color.neutral9
+            color: root.subtextColor
             text: root.subtext
             horizontalAlignment: root.center ? Text.AlignHCenter : Text.AlignLeft
             wrapMode: wrap ? Text.WordWrap : Text.NoWrap

src/qml/controls/Setting.qml

@@ -13,6 +13,8 @@ AbstractButton {
     property alias actionItem: action_loader.sourceComponent
     property alias loadedItem: action_loader.item
     property string description
+    property string errorText: ""
+    property bool showErrorText: false
     property color stateColor
     hoverEnabled: true
     state: "FILLED"
@@ -75,6 +77,8 @@ AbstractButton {
             description: root.description
             descriptionSize: 15
             descriptionMargin: 0
+            subtext: root.showErrorText ? root.errorText : ""
+            subtextColor: Theme.color.blue
         }
         Loader {
             id: action_loader

src/qml/controls/ValueInput.qml

@@ -14,6 +14,8 @@ TextInput {
     property color textColor: root.filled ? Theme.color.neutral9 : Theme.color.neutral5
     enabled: true
     state: root.parentState
+    validator: IntValidator{}
+    maximumLength: 5
 
     states: [
         State {
@@ -48,4 +50,12 @@ TextInput {
     Behavior on color {
         ColorAnimation { duration: 150 }
     }
+
+    function checkValidity(minVal, maxVal, input) {
+        if (input < minVal || input > maxVal) {
+            return false
+        } else {
+            return true
+        }
+    }
 }

src/qml/options_model.h

@@ -5,7 +5,10 @@
 #ifndef BITCOIN_QML_OPTIONS_MODEL_H
 #define BITCOIN_QML_OPTIONS_MODEL_H
 
+#include <txdb.h>
 #include <util/settings.h>
+#include <util/system.h>
+#include <validation.h>
 
 #include <QObject>
 
@@ -19,6 +22,10 @@ class OptionsQmlModel : public QObject
     Q_OBJECT
     Q_PROPERTY(int dbcacheSizeMiB READ dbcacheSizeMiB WRITE setDbcacheSizeMiB NOTIFY dbcacheSizeMiBChanged)
     Q_PROPERTY(bool listen READ listen WRITE setListen NOTIFY listenChanged)
+    Q_PROPERTY(int maxDbcacheSizeMiB READ maxDbcacheSizeMiB CONSTANT)
+    Q_PROPERTY(int minDbcacheSizeMiB READ minDbcacheSizeMiB CONSTANT)
+    Q_PROPERTY(int maxScriptThreads READ maxScriptThreads CONSTANT)
+    Q_PROPERTY(int minScriptThreads READ minScriptThreads CONSTANT)
     Q_PROPERTY(bool natpmp READ natpmp WRITE setNatpmp NOTIFY natpmpChanged)
     Q_PROPERTY(bool prune READ prune WRITE setPrune NOTIFY pruneChanged)
     Q_PROPERTY(int pruneSizeGB READ pruneSizeGB WRITE setPruneSizeGB NOTIFY pruneSizeGBChanged)
@@ -33,6 +40,10 @@ class OptionsQmlModel : public QObject
     void setDbcacheSizeMiB(int new_dbcache_size_mib);
     bool listen() const { return m_listen; }
     void setListen(bool new_listen);
+    int maxDbcacheSizeMiB() const { return m_max_dbcache_size_mib; }
+    int minDbcacheSizeMiB() const { return m_min_dbcache_size_mib; }
+    int maxScriptThreads() const { return m_max_script_threads; }
+    int minScriptThreads() const { return m_min_script_threads; }
     bool natpmp() const { return m_natpmp; }
     void setNatpmp(bool new_natpmp);
     bool prune() const { return m_prune; }
@@ -61,7 +72,11 @@ class OptionsQmlModel : public QObject
 
     // Properties that are exposed to QML.
     int m_dbcache_size_mib;
+    const int m_min_dbcache_size_mib{nMinDbCache};
+    const int m_max_dbcache_size_mib{nMaxDbCache};
     bool m_listen;
+    const int m_max_script_threads{MAX_SCRIPTCHECK_THREADS};
+    const int m_min_script_threads{-GetNumCores()};
     bool m_natpmp;
     bool m_prune;
     int m_prune_size_gb;