Change background of google slides shape to red - google-slides-api

Question

I am trying to find the answer in Google Slides API references for how to set the background color of a shape I have in my Google Slide. I have given it the title (using Alt Text feature) "rectangle1", so my intention is to write the code along the lines of "if shape's property "title" == "rectangle1", then set background color to red."
I can't see a single reference to "SetBackgroundFill" or SetBackgroundColor, or anything of that sort.
Is it possible?

Answer 1

This is another possible answer, using a so-called "container bound script", which is only accessible through the specific Slide's Tools/Script Editor menu (no other way, or else it won't work).
I found that this "container bound script" approach gives me more power over my slide, and it avoids these expensive calls to "batchUpdate", when using "stand alone" scripts as in my other "self-answer".
So, in a way, I recommend it to myself, but, perhaps, to someone else, my other approach would be a better choice.
For one thing, this approach has a much faster response time.
var hex_color = '#54BdeF';
function test1() {
var selection = SlidesApp.getActivePresentation().getSelection();
var currentPage = selection.getCurrentPage();
var selectionType = selection.getSelectionType();
var shapes = currentPage.getShapes();
for (i=0; i < shapes.length; i++) {
if (shapes[i].getTitle() == 'rectangle1') {
shape_fill = shapes[i].getFill();
shape_fill.setSolidFill(hex_color);
}
}
}
Again, as before, I would welcome any comments and suggestions.

Answer 2

To set background color, you need Element Operations.
The Slides API allows you to create and edit a variety of page
elements, including text boxes, images, tables, basic shapes, lines,
and embedded videos. The examples on this page show some common page
element operations that can be achieved with the API.
Following the steps specified here will do the changes in your specified shape or element. Check the example.

Answer 3

Well, here is my solution. If someone sees a way to improve it, I am all ears, but so far, it appears to work for me glitch-free.
First, I find the shape I am after using the following logic:
function ChangeColorMain()
{
ChangeShapeBackgroundColor('title', 'rectangle1', color_to_repl_r, color_to_repl_g, color_to_repl_b, alpha_value );
}
function ChangeShapeBackgroundColor(shape_property_name, shape_property_value, color_to_set_r, color_to_set_g, color_to_set_b) {
Logger.log( 'ChangeShapeBackgroundColor(shape_property_name=%s, shape_property_value=%s, color_to_set_r=%s, color_to_set_g=%s, color_to_set_b=%s) ',
shape_property_name, shape_property_value, color_to_set_r, color_to_set_g, color_to_set_b);
var presentation = Slides.Presentations.get(presentationId);
var slides = presentation.slides;
Logger.log('The presentation contains %s slides:', slides.length);
for (i = 0; i < slides.length; i++) {
for (j = 0; j < slides[i].pageElements.length; j++ ) {
if (shape_property_name == 'title' && shape_property_value == slides[i].pageElements[j].title) {
Logger.log('Found it');
//slides[i].pageElements[j].shape.shapeProperties.shapeBackgroundFill.solidFill.color.rgbColor.red = color_to_set_r;
SubmitRequest(slides[i].pageElements[j].objectId, color_to_set_r, color_to_set_g, color_to_set_b, alpha_value);
}
} //end of for that iterates through every element
}
}
So, you'll notice that I start my process by calling the function "ChangeColorMain" which also gets my global variables color_to_repl_r... which are defined in a different file of my google script project, but that's not important.
Once inside the ChangeShapeBackgroundColor(), I iterate through all "PageElements" on my slide (see the relevant for loops) and use if statements to check if I got to the shape I am looking for. Finally, once I have located it, I call the all important function SubmitRequest(), which is "expensive". You can't make too many calls in one day, or else Google blocks this function until the day ends. But not a problem if you are making less than 500 calls per day (this number might be wrong/might change).
Here are the details of "SubmitRequest()" which I was able to create by finally figuring out how to make sense of this reference page:
https://developers.google.com/slides/reference/rest/v1/presentations/request#UpdateShapePropertiesRequest
function SubmitRequest(shape_id, r, g, b, a) {
var rgb_color = {
red: r,
green: g,
blue: b
};
var opaque_color = {
rgbColor: rgb_color
};
var solid_fill = {
color: opaque_color,
alpha: a
};
var background_fill = {
solidFill: solid_fill
};
var shape_properties = {
shapeBackgroundFill: background_fill
};
var update_request = {
objectId: shape_id,
shapeProperties: shape_properties,
fields: "shapeBackgroundFill.solidFill.color"
};
var requests = [{
updateShapeProperties: update_request
}];
// Execute the request.
var batch_update_return = Slides.Presentations.batchUpdate({
requests: requests
}, presentationId);
Logger.log(
'This is what you get from Google after submitting batchUpdate request:\n%s', batch_update_return);
}