Ok, here's basically how I do it in my player window. The example uses Screen items, but it's really better to replace some of the Screen items with LayoutBox items. In my mod, I like to put the pet health right underneath the pet bar.
Most of the action is in Player_PetFixer, because it has a Layout. Try to ignore Player_PetHolder at first, it's merely the container for Player_PetFixer.
The label items Player_PetSpacer1 and Player_PetSpacer2 kinda just cancel each other out, but they do serve a purpose. I use a negative 3 in Player_PetSpacer2 to make the percentage partially-overlap the gauge. (Normally in a vertical layout the items are placed in order, each one below the last). But then I had to add Player_PetSpacer1 to make sure that the sum of the heights doesn't actually go below zero -- that would cause errors.
The pet percent is Player_PetHealthLabel. When you have a pet, it's located at 1,30 within Player_PetFixer, because the gauge has height of 30. (3+30-3) When you don't have a pet, it's located at 1,0 within Player_PetFixer because the gauge is not displayed, essentially height of 0. (3+0-3)
But Player_PetFixer itself is located at a Y coord of -17, so Player_PetHealthLabel is displayed at location 1,13 or location 1,-17 within Player_PetHolder. In the latter case the little '0' DOES still show, but since it's at a negative location you can't actually see it.
<Gauge item = "Pet_HP">
<ScreenID>PetHP</ScreenID>
<Font>3</Font>
<TextColor>
<R>240</R>
<G>240</G>
<B>240</B>
</TextColor>
<RelativePosition>true</RelativePosition>
<Location>
<X>0</X>
<Y>0</Y>
</Location>
<Size>
<CX>100</CX>
<CY>30</CY>
</Size>
<TextOffsetY>-50</TextOffsetY>
<GaugeOffsetY>28</GaugeOffsetY>
<Style_VScroll>false</Style_VScroll>
<Style_HScroll>false</Style_HScroll>
<Style_Transparent>false</Style_Transparent>
<!--<TooltipReference/>-->
<FillTint>
<R>51</R>
<G>192</G>
<B>51</B>
</FillTint>
<LinesFillTint>
<R>220</R>
<G>220</G>
<B>0</B>
</LinesFillTint>
<DrawLinesFill>false</DrawLinesFill>
<EQType>16</EQType>
<GaugeDrawTemplate>
<Background>A_PW_ThinGaugeBackground</Background>
<Fill>A_PW_ThinGaugeFill</Fill>
<!--<Lines>A_PW_ThinGaugeLines</Lines>-->
<!--<LinesFill>A_PW_ThinGaugeLinesFill</LinesFill>-->
</GaugeDrawTemplate>
</Gauge>
<Label item ="Player_PetHealthLabel">
<ScreenID>PetHealthLabel</ScreenID>
<Font>2</Font>
<RelativePosition>true</RelativePosition>
<Location>
<X>3</X>
<Y>0</Y>
</Location>
<Size>
<CX>20</CX>
<CY>11</CY>
</Size>
<Text></Text>
<EQType>69</EQType>
<TextColor>
<R>255</R>
<G>255</G>
<B>255</B>
</TextColor>
<NoWrap>true</NoWrap>
<AlignCenter>true</AlignCenter>
<AlignRight>false</AlignRight>
<Style_Tooltip>false</Style_Tooltip>
</Label>
<LayoutVertical item="Player_L_Ver0">
<Padding>0</Padding>
<Resize>false</Resize>
</LayoutVertical>
<LayoutHorizontal item="Player_L_Hor0">
<Padding>0</Padding>
<Resize>false</Resize>
</LayoutHorizontal>
<Label item="Player_PetSpacer1">
<Size><CX>0</CX><CY>3</CY></Size>
<Style_Tooltip>false</Style_Tooltip>
</Label>
<Label item="Player_PetSpacer2">
<Size><CX>0</CX><CY>-3</CY></Size>
<Style_Tooltip>false</Style_Tooltip>
</Label>
<Label item="Player_PetSpacer3">
<Size><CX>1</CX><CY>0</CY></Size>
<Style_Tooltip>false</Style_Tooltip>
</Label>
<Screen item="Player_PetPctHolder">
<RelativePosition>true</RelativePosition>
<Layout>Player_L_Hor0</Layout>
<Style_Transparent>true</Style_Transparent>
<Style_Border>false</Style_Border>
<Style_Tooltip>false</Style_Tooltip>
<DrawTemplate>WDT_PW_RoundedNoTitle</DrawTemplate>
<Location>
<X>0</X>
<Y>-17</Y>
</Location>
<Size>
<CX>105</CX>
<CY>65</CY>
</Size>
<Pieces>Player_PetSpacer3</Pieces>
<Pieces>Player_PetHealthLabel</Pieces>
</Screen>
<Screen item="Player_PetFixer">
<RelativePosition>true</RelativePosition>
<Layout>Player_L_Ver0</Layout>
<Style_Transparent>true</Style_Transparent>
<Style_Border>false</Style_Border>
<DrawTemplate>WDT_PW_RoundedNoTitle</DrawTemplate>
<Location>
<X>0</X>
<Y>-17</Y>
</Location>
<Size>
<CX>105</CX>
<CY>65</CY>
</Size>
<Pieces>Player_PetSpacer1</Pieces>
<Pieces>Pet_HP</Pieces>
<Pieces>Player_PetSpacer2</Pieces>
<Pieces>Player_PetPctHolder</Pieces>
</Screen>
<Screen item="Player_PetHolder">
<RelativePosition>true</RelativePosition>
<Style_Transparent>true</Style_Transparent>
<Style_Border>false</Style_Border>
<DrawTemplate>WDT_PW_RoundedNoTitle</DrawTemplate>
<Location>
<X>2</X>
<Y>17</Y>
</Location>
<Size>
<CX>100</CX>
<CY>24</CY>
</Size>
<Pieces>Player_PetFixer</Pieces>
</Screen>
Hiding with containers
Linear Mode
