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Lesson_69

README.md

In this lesson we will look at several built-in VFR conditionals.

Before we go deep into these new keywords, let's look one more time at our form:

Before

Remember it as a reference as we would change the look of our form in this lesson.

Also each of the built-in`s in this lesson works with a conditional statement. But we want to show how the element works, so we would simply use a constant TRUE in the place of a conditional.

suppressif

The suppress tag causes the nested objects to be hidden from the user if the expression appearing as the first nested object evaluates to TRUE.

Opcode for this operation is:

#define EFI_IFR_SUPPRESS_IF_OP 0x0a

VFR token definition can be found under a link https://edk2-docs.gitbook.io/edk-ii-vfr-specification/2_vfr_description_in_bnf/211_vfr_form_definition#2.11.7.3-vfr-statement-suppressif-definition

As an example let's suppress our orderedlist element:

suppressif TRUE;
    orderedlist
      ...
    endlist;
endif;

After that the form would look like this:

SuppressIf

So the element simply has become invisible for the user.

One more use of suppressif is in the fact that you can hide options inside the question.

For example currently our oneof question looks like this:

SuppressIf_oneof1

But adding suppressif to the option 3:

oneof
  varid = FormData.OneOfValue,
  prompt = STRING_TOKEN(ONEOF_PROMPT),
  help = STRING_TOKEN(ONEOF_HELP),
  option text = STRING_TOKEN(ONEOF_OPTION1), value = 0x00, flags = 0;
  option text = STRING_TOKEN(ONEOF_OPTION2), value = 0x33, flags = 0;
  suppressif TRUE;
  option text = STRING_TOKEN(ONEOF_OPTION3), value = 0x55, flags = 0;
  endif;
endoneof;

Would hide it for the selection:

SuppressIf_oneof2

grayoutif

All nested statements or questions will be grayed out (not selectable and visually distinct) if the expression appearing as the first nested object evaluates to TRUE.

Opcode for this operation is:

#define EFI_IFR_GRAY_OUT_IF_OP 0x19

VFR token definition can be found under a link https://edk2-docs.gitbook.io/edk-ii-vfr-specification/2_vfr_description_in_bnf/211_vfr_form_definition#2.11.7.4-vfr-statement-grayoutif-definition

As an example let's grayout our orderedlist element:

grayoutif TRUE;
    orderedlist
      ...
    endlist;
endif;

As a result the element becomes unselectable like subtitle:

GrayoutIf

disableif

All nested statements, questions, options or expressions will not be processed if the expression appearing as the first nested object evaluates to TRUE.

Opcode for this operation is:

#define EFI_IFR_DISABLE_IF_OP 0x1E

VFR token definition can be found under a link https://edk2-docs.gitbook.io/edk-ii-vfr-specification/2_vfr_description_in_bnf/211_vfr_form_definition#2.11.7.2-vfr-statement-disalbeif-definition

As an example let's disable our orderedlist element:

disableif TRUE;
    orderedlist
      ...
    endlist;
endif

With this condition our form looks like in a suppressif example, the element is simply not present in the view:

DisableIf

warningif

Creates a validation expression and warning message for a question.

Opcode for this operation is:

#define EFI_IFR_WARNING_IF_OP 0x63

VFR token definition can be found under a link https://edk2-docs.gitbook.io/edk-ii-vfr-specification/2_vfr_description_in_bnf/211_vfr_form_definition#2.11.6.1.7-vfr-question-tag-warningif-definition-vfrstatement

This built-in is supposed to be used inside a question. Let's add it to the orderedlist:

orderedlist
  varid = FormData.OrderedListValue,
  prompt = STRING_TOKEN(ORDERED_LIST_PROMPT),
  help = STRING_TOKEN(ORDERED_LIST_HELP),
  option text = STRING_TOKEN(ORDERED_LIST_OPTION1), value = 0x0A, flags = 0;
  option text = STRING_TOKEN(ORDERED_LIST_OPTION2), value = 0x0B, flags = 0;
  option text = STRING_TOKEN(ORDERED_LIST_OPTION3), value = 0x0C, flags = 0;
  warningif
    prompt = STRING_TOKEN(WARNING_IF_PROMPT),
    TRUE
  endif;
endlist;

Add new string to the UefiLessonsPkg/HIIFormDataElements/Strings.uni

#string WARNING_IF_PROMPT      #language en-US  "WarningIf prompt"

The warning message appear when you change the variable and hit enter:

WarningIf

But it is important to notice, that you can ignore the warning and still save the updated data with F10.

With warningif it is possible to set timeout value for the warning message:

warningif
  prompt = STRING_TOKEN(WARNING_IF_PROMPT),
  timeout = 5,
  TRUE
endif;

In this case warning will dissapear after 5 seconds (or earlier if user presses a kay to acknowledge change). The ticking timer will be displayed on the popup window:

WarningIf_timeout

nosubmitif

Creates a conditional expression which will be evaluated when the form is submitted. If the conditional evaluates to TRUE, then the error message Error will be displayed to the user and the user will be prevented from submitting the form.

Opcode for this operation is:

#define EFI_IFR_NO_SUBMIT_IF_OP 0x10

VFR token definition can be found under a link https://edk2-docs.gitbook.io/edk-ii-vfr-specification/2_vfr_description_in_bnf/211_vfr_form_definition#2.11.6.1.2-vfr-question-tag-nosubmitif-definition

This built-in is supposed to be used inside a question. Let's add it to the orderedlist:

orderedlist
  varid = FormData.OrderedListValue,
  prompt = STRING_TOKEN(ORDERED_LIST_PROMPT),
  help = STRING_TOKEN(ORDERED_LIST_HELP),
  option text = STRING_TOKEN(ORDERED_LIST_OPTION1), value = 0x0A, flags = 0;
  option text = STRING_TOKEN(ORDERED_LIST_OPTION2), value = 0x0B, flags = 0;
  option text = STRING_TOKEN(ORDERED_LIST_OPTION3), value = 0x0C, flags = 0;
  nosubmitif
    prompt = STRING_TOKEN(NOSUBMIT_IF_PROMPT),
    TRUE
  endif;
endlist;

Add new string to the UefiLessonsPkg/HIIFormDataElements/Strings.uni

#string NOSUBMIT_IF_PROMPT     #language en-US  "NoSubmitIf prompt"

With this code you can still change the variable and hit enter and the form would display updated value with Configuration changed message. But the form submit (F10) would fail. It is not possible to save variable if nosubmitif condition evaluates to TRUE.

NosubmitIf

inconsistentif

Creates a validation expression and error message for a question. The user should not be allowed to submit the results of a form inconsistency.

VFR token definition can be found under a link https://edk2-docs.gitbook.io/edk-ii-vfr-specification/2_vfr_description_in_bnf/211_vfr_form_definition#2.11.6.1.1-vfr-question-tag-inconsistentif-definition

Opcode for this operation is:

#define EFI_IFR_INCONSISTENT_IF_OP 0x011

This built-in is supposed to be used inside a question. Let's add it to the orderedlist:

orderedlist
  varid = FormData.OrderedListValue,
  prompt = STRING_TOKEN(ORDERED_LIST_PROMPT),
  help = STRING_TOKEN(ORDERED_LIST_HELP),
  option text = STRING_TOKEN(ORDERED_LIST_OPTION1), value = 0x0A, flags = 0;
  option text = STRING_TOKEN(ORDERED_LIST_OPTION2), value = 0x0B, flags = 0;
  option text = STRING_TOKEN(ORDERED_LIST_OPTION3), value = 0x0C, flags = 0;
  inconsistentif
    prompt = STRING_TOKEN(INCONSISTENT_IF_PROMPT),
    TRUE
  endif;
endlist;

Add new string to the UefiLessonsPkg/HIIFormDataElements/Strings.uni

#string INCONSISTENT_IF_PROMPT #language en-US  "InconsistentIf prompt"

This code won't allow to change a variable to the value when inconsistentif evaluates to TRUE. Form will simply show popup message and won't change values.

InconsistentIf