fix gasLimit default and allow still using gas estimate

libs/remix-lib/src/execution/txRunnerWeb3.ts

@@ -141,10 +141,15 @@ export class TxRunnerWeb3 {
             * gasLimit is a value that can be set in the UI to hardcap value that can be put in a tx.
             * e.g if the gasestimate 
             */
-            if (gasEstimation > gasLimit) {
+            if (gasLimit !== '0x0' && gasEstimation > gasLimit) {
               return callback(`estimated gas for this transaction (${gasEstimation}) is higher than gasLimit set in the configuration  (${gasLimit}). Please raise the gas limit.`)
-            }
-            tx['gas'] = gasLimit
+            } 
+            
+            if (gasLimit === '0x0') {
+              tx['gas'] = gasEstimation
+            } else {
+              tx['gas'] = gasLimit
+            }           
 
             if (this._api.config.getUnpersistedProperty('doNotShowTransactionConfirmationAgain')) {
               return this._executeTx(tx, network, null, this._api, promptCb, callback)

libs/remix-ui/run-tab/src/lib/components/gasLimit.tsx

@@ -0,0 +1,44 @@
+// eslint-disable-next-line no-use-before-define
+import {CustomTooltip} from '@remix-ui/helper'
+import React, { useEffect, useRef } from 'react'
+import {FormattedMessage} from 'react-intl'
+import {GasPriceProps} from '../types'
+
+const defaultGasLimit = 500000
+export function GasLimitUI(props: GasPriceProps) {
+  const auto = useRef(true)
+  const inputComponent = useRef<HTMLInputElement>(null)
+  const currentGasLimit = useRef(defaultGasLimit)
+
+  useEffect(() => {
+    handleGasLimitAuto(true)
+  }, [])
+
+  const handleGasLimit = (e) => {
+    props.setGasFee(e.target.value)
+  }
+
+  const handleGasLimitAuto = (checked) => {
+    auto.current = checked
+    if (checked) {
+      currentGasLimit.current = parseInt(inputComponent.current.value)
+      props.setGasFee(0)
+    } else {
+      props.setGasFee(currentGasLimit.current)
+    }    
+  }
+
+  return (
+    <div className="udapp_crow">
+      <label className="udapp_settingsLabel">
+        <FormattedMessage id="udapp.gasLimit" />
+      </label>
+      <div className='custom-control custom-checkbox udapp_col2 udapp_gasNval'>
+        <input type="checkbox" className="" id="gasLimitAuto" checked={auto.current} onChange={(e) => { handleGasLimitAuto(e.target.checked) } } />
+        <CustomTooltip placement={'right'} tooltipClasses="text-nowrap" tooltipId="remixGasPriceTooltip" tooltipText={<FormattedMessage id="udapp.tooltipText4" />}>
+          <input type="number" ref={inputComponent} disabled={auto.current} className="form-control" id="gasLimit" value={props.gasLimit === 0 ? currentGasLimit.current : props.gasLimit} onChange={handleGasLimit} />        
+        </CustomTooltip>        
+      </div>      
+    </div>
+  )
+}

libs/remix-ui/run-tab/src/lib/components/gasPrice.tsx

@@ -1,22 +0,0 @@
-// eslint-disable-next-line no-use-before-define
-import {CustomTooltip} from '@remix-ui/helper'
-import React from 'react'
-import {FormattedMessage} from 'react-intl'
-import {GasPriceProps} from '../types'
-
-export function GasPriceUI(props: GasPriceProps) {
-  const handleGasLimit = (e) => {
-    props.setGasFee(e.target.value)
-  }
-
-  return (
-    <div className="udapp_crow">
-      <label className="udapp_settingsLabel">
-        <FormattedMessage id="udapp.gasLimit" />
-      </label>
-      <CustomTooltip placement={'right'} tooltipClasses="text-nowrap" tooltipId="remixGasPriceTooltip" tooltipText={<FormattedMessage id="udapp.tooltipText4" />}>
-        <input type="number" className="form-control udapp_gasNval udapp_col2" id="gasLimit" value={props.gasLimit} onChange={handleGasLimit} />
-      </CustomTooltip>
-    </div>
-  )
-}

libs/remix-ui/run-tab/src/lib/components/settingsUI.tsx

@@ -4,7 +4,7 @@ import {SettingsProps} from '../types'
 import {EnvironmentUI} from './environment'
 import {NetworkUI} from './network'
 import {AccountUI} from './account'
-import {GasPriceUI} from './gasPrice'
+import {GasLimitUI} from './gasLimit'
 import {ValueUI} from './value'
 
 export function SettingsUI(props: SettingsProps) {
@@ -27,7 +27,7 @@ export function SettingsUI(props: SettingsProps) {
         signMessageWithAddress={props.signMessageWithAddress}
         passphrase={props.passphrase}
       />
-      <GasPriceUI gasLimit={props.gasLimit} setGasFee={props.setGasFee} />
+      <GasLimitUI gasLimit={props.gasLimit} setGasFee={props.setGasFee} />
       <ValueUI setUnit={props.setUnit} sendValue={props.sendValue} sendUnit={props.sendUnit} setSendValue={props.setSendValue} />
     </div>
   )

libs/remix-ui/run-tab/src/lib/reducers/runTab.ts

@@ -18,7 +18,7 @@ export const runTabInitialState: RunTabState = {
   },
   sendValue: '0',
   sendUnit: 'wei',
-  gasLimit: 500000,
+  gasLimit: 0,
   selectExEnv: 'vm-paris',
   personalMode: false,
   networkName: 'VM',