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How to detect if the penInput is blank or empty

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Hi,

I want to have a pen input to collect a signature, check if the penInput is empty or blank and doing some flows actions. I try this https://powerusers.microsoft.com/t5/General-Discussion/How-do-you-determine-if-Pen-Input-is-blank/td-p/84079 from @Shanescows on a form called when you are on a list SharePoint and it's working great! But when i create my application and want to use it, it's not really work.

To understand why i have this problem, i create two inputs to check my values :

- TextInput2 → On the default data, i set my var BlankImage (created on my EditScreen1 on parameter "OnVisible" with

UpdateContext({BlankImage : MyDoodles.Image})

)

- TextInput4 → On default data, i set the value MyDoodles.Image.

When I run my application, you can see two blobmanager URLs, where blue line is for my TextInput4 and the other for TextInput2 (my PenInput is empty, I haven't written anything on but i have 2 different URLs).

I don't want to let my user use or click on any button, his job is to sign my form, write some information in and valid his form. After my function check if the penInput is empty or not and doing some actions in terms of the response.

Thanks for your help.

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h-nagao 392 on at

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Hi,
To compair "blank" image and filled image, I have used JSON(PenInput.Image, IncludeBinaryData).
JSON(PenInput.Image, IncludeBinaryData) produces data uri of image and compair default data uri and current one, I could detect PenInput is empty.
*Timer control is monitoring pen input image.

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v-xida-msft Microsoft Employee on at

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Hi @Anonymous ,

Do you want to detect if the Pen Input control is empty?

Currently, within PowerApps, there is no direct way to detect if a Pen Input control is empty. Even though, you do not draw anything within the Pen Input control (The Pen Input control is Blank), the result the PenInput1.Image formula would still return a blob data (e.g. appres://blobmanager/b8c2a7250f344b148a9a0dfd19e7a6a0/3) rather than empty.

Within the solution mentioned by @Shanescows, it store the PenInput1.Image result into a variable as Blank Pen Input when you load your Pen Input screen first time. If you draw anything within the Pen Input control, the result the PenInput1.Image formula returned would be different from the variable value you set up before.

So you could compare the current PenInput1.Image result with the stored variable, to detect if the Pen Input control is "Blank" (You do not draw anything within the Pen Input control).

Please consider set the OnVisible property of the screen which contains the Pen Input control to following:

Reset(PenInput1); UpdateContext({BlankBlobData: PenInput1.Image})

If you want to detect if the Pen Input control is "Blank" (you do not draw anything within the Pen Input control), please use the following formula:

If( PenInput1.Image = BlankBlobData, "Pen Input control is Blank. You do not draw anything within it", "Pen Input control is not Blank. You have drawn something within it" )

Please consider take a try with above solution, check if the issue is solved.

Best regards,

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Community Power Pla... Microsoft Employee on at

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Hi thanks for your help,

I test each of your propositions and not really work as I want 😞

@v-xida-msft, I tested to put my Reset(penInput1) on my screen (EditScreen) after my UpdateContext (just to check and understand how this is work).

When I do this, and I click on my button to have access to my EditScreen, my blob data change 2 times (My UpdateContext return this : appres://blobmanager/b8c2a7250f344b148a9a0dfd19e7a6a0/3 and my penInput1.Image return this : appres://blobmanager/b8c2a7250f344b148a9a0dfd19e7a6a0/5).

So, I think the reset method change the value of your penInput1 (you can see the value input change when you click on the clean/reset button when your showControls is true).

I remove all my Reset(penInput1) except the one on the onVisible parameter, but the problem has not gone.

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h-nagao 392 on at

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How about JSON approach?

I have tested on my side, and it’s working fine.

For OnVisible property:
Reset(PenInput1);
UpdateContext({BlankBlobData: JSON(PenInput1.Image, IncludeBinaryData)})

and some label text:
If(
JSON(PenInput1.Image,IncludeBinaryData) = BlankBlobData,
"Pen Input control is Blank. You do not draw anything within it",
"Pen Input control is not Blank. You have drawn something within...”)

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Community Power Pla... Microsoft Employee on at

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Hi, I was testing with JSON method, modify where I call it (on my iconButton, onSelect), and now, working perfectly.

Thanks for your help.

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newbie101 44 on at

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Thanks for the solutions above. Here is a simpler solution.

For App, onStart = Set(varBlank, true)
For PenInput1 control,
ShowControls = false
onSelect = Set(varBlank, false)
Add a button on top of PenInput1 control, onSelect = Reset(PenInput1); Set(varBlank, true)

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Hor 38 on at

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The formula

If(
JSON(PenInput1.Image,IncludeBinaryData) = BlankBlobData,
"Pen Input control is Blank. You do not draw anything within it",
"Pen Input control is not Blank. You have drawn something within...”)

shows error "behavior function in a non-behavior property. you cant use this property to change values elsewhere in the app.". Could you help please?

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h-nagao 392 on at

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Hi Hor,

It is not able to compare JSON() result directly with others.
Before If operation, Set to some variable, i.e., Set(xxxx, JSON(PenInput1.Image,IncludeBinaryData));

Then If(IsBlank(xxxx),.....) , it allows to detect Blank Input or not.

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Hor 38 on at

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Hi

Sorry Im confused, where should I set the variable? I couldnt set the variable at the text label.

On the other hand, does this method also detect if the PenInput control is empty after the "X" button is clicked?

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DragonLord 200 on at

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this simply does not work.

message is still shows error "behavior function in a non-behavior property. you cant use this property to change values elsewhere in the app."

is this a bug?

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